don't include VSL.Versions.targets multiple times

ProducesNoOutput.Settings.targets already imports it

src/Setup/DevDivVsix/CompilersPackage/Microsoft.CodeAnalysis.Compilers.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>

src/Setup/DevDivVsix/CompilersPackage/Microsoft.CodeAnalysis.Compilers.vsmanproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <FinalizeManifest>true</FinalizeManifest>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/Microsoft.CodeAnalysis.LanguageServices.vsmanproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="15.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <FinalizeManifest>true</FinalizeManifest>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/MicrosoftCodeAnalysisExpressionEvaluator/Microsoft.CodeAnalysis.ExpressionEvaluator.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/MicrosoftCodeAnalysisVisualStudioInteractiveComponents/Microsoft.CodeAnalysis.VisualStudioInteractiveComponents.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/MicrosoftCodeAnalysisVisualStudioInteractiveWindow/Microsoft.CodeAnalysis.VisualStudioInteractiveWindow.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/MicrosoftCodeAnalysisVisualStudioSetup/Microsoft.CodeAnalysis.VisualStudio.Setup.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/MicrosoftCodeAnalysisVisualStudioSetupInteractive/Microsoft.CodeAnalysis.VisualStudio.Setup.Interactive.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/MicrosoftCodeAnalysisVisualStudioSetupNext/Microsoft.CodeAnalysis.VisualStudio.Setup.Next.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>

src/Setup/DevDivVsix/MicrosoftCodeAnalysisLanguageServices/MicrosoftCodeAnalysisVisualStudioTelemetry/Microsoft.CodeAnalysis.VisualStudio.Telemetry.swixproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\..\..\..\build\Targets\ProducesNoOutput.Settings.targets" />
-  <Import Project="..\..\..\..\..\build\Targets\VSL.Versions.targets" />
 
   <PropertyGroup>
     <OutputArchitecture>neutral</OutputArchitecture>