Update Microsoft.VisualStudio.ProjectSystem package version

We need this version to avoid conflicts with other assemblies that
reference a different version of the System.Composition.* assemblies.

build/Targets/Packages.props

@@ -89,7 +89,7 @@
     <MicrosoftVisualStudioProgressionCodeSchemaVersion>15.0.26507-alpha</MicrosoftVisualStudioProgressionCodeSchemaVersion>
     <MicrosoftVisualStudioProgressionCommonVersion>15.0.26507-alpha</MicrosoftVisualStudioProgressionCommonVersion>
     <MicrosoftVisualStudioProgressionInterfacesVersion>15.0.26507-alpha</MicrosoftVisualStudioProgressionInterfacesVersion>
-    <MicrosoftVisualStudioProjectSystemVersion>15.0.751</MicrosoftVisualStudioProjectSystemVersion>
+    <MicrosoftVisualStudioProjectSystemVersion>15.3.178-pre-g209fb07c2e</MicrosoftVisualStudioProjectSystemVersion>
     <MicrosoftVisualStudioQualityToolsUnitTestFrameworkVersion>10.0.0.0-alpha</MicrosoftVisualStudioQualityToolsUnitTestFrameworkVersion>
     <MicrosoftVisualStudioRemoteControlVersion>14.0.249-master2E2DC10C</MicrosoftVisualStudioRemoteControlVersion>
     <MicrosoftVisualStudioSetupConfigurationInteropVersion>1.3.269-rc</MicrosoftVisualStudioSetupConfigurationInteropVersion>