Update dependencies from https://github.com/dotnet/winforms build 20211218.1 (#5851)

[main] Update dependencies from dotnet/winforms

eng/Version.Details.xml

 <?xml version="1.0" encoding="utf-8"?>
 <Dependencies>
   <ProductDependencies>
-    <Dependency Name="Microsoft.Private.Winforms" Version="7.0.0-alpha.1.21616.1">
+    <Dependency Name="Microsoft.Private.Winforms" Version="7.0.0-alpha.1.21618.1">
       <Uri>https://github.com/dotnet/winforms</Uri>
-      <Sha>76dedba0e22119fb170098b51911a83ab004c1ee</Sha>
+      <Sha>6766f3edf0ab99bf64aa0243f6125caa5fba7344</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.Dotnet.WinForms.ProjectTemplates" Version="7.0.0-alpha.1.21616.1">
+    <Dependency Name="Microsoft.Dotnet.WinForms.ProjectTemplates" Version="7.0.0-alpha.1.21618.1">
       <Uri>https://github.com/dotnet/winforms</Uri>
-      <Sha>76dedba0e22119fb170098b51911a83ab004c1ee</Sha>
+      <Sha>6766f3edf0ab99bf64aa0243f6125caa5fba7344</Sha>
     </Dependency>
     <Dependency Name="System.CodeDom" Version="7.0.0-alpha.1.21606.7" CoherentParentDependency="Microsoft.Private.Winforms">
       <Uri>https://github.com/dotnet/runtime</Uri>

eng/Versions.props

@@ -9,7 +9,7 @@
   </PropertyGroup>
   <!-- NuGet Package Versions -->
   <PropertyGroup>
-    <MicrosoftPrivateWinformsVersion>7.0.0-alpha.1.21616.1</MicrosoftPrivateWinformsVersion>
+    <MicrosoftPrivateWinformsVersion>7.0.0-alpha.1.21618.1</MicrosoftPrivateWinformsVersion>
   </PropertyGroup>
   <!-- Packages that come from https://github.com/dotnet/coreclr -->
   <PropertyGroup>