[Infra] Bump System.Collections.Immutable for 5.0.0 to 6.0.0

Author: reegeek

src/Directory.Build.props

@@ -7,7 +7,7 @@
  <!-- common tests properties -->
  <PropertyGroup Condition="$(MSBuildProjectName.EndsWith('Tests'))">
  <IsPackable>False</IsPackable>
- <DefaultTargetFrameworks>net50;net48;net60</DefaultTargetFrameworks>
+ <DefaultTargetFrameworks>net60;net50;net48</DefaultTargetFrameworks>
  </PropertyGroup>
 
  <ItemGroup Condition="$(MSBuildProjectName.EndsWith('Tests'))">

src/StructLinq/StructLinq.csproj

@@ -2,6 +2,8 @@
 
  <PropertyGroup>
  <TargetFrameworks>netstandard1.1;net452;net472;net48;netcoreapp2.1;netcoreapp2.2;netcoreapp3.0;netcoreapp3.1;net50;net60</TargetFrameworks>
+<OldVersion>True</OldVersion>
+<OldVersion Condition="'$(TargetFramework)' == 'netstandard1.1' Or '$(TargetFramework)' == 'net452'">true</OldVersion>
  </PropertyGroup>
 
  <PropertyGroup Label="Nuget">
@@ -19,8 +21,10 @@
  <PrivateAssets>all</PrivateAssets>
  </PackageReference>
  <PackageReference Include="System.Buffers" Version="4.5.1" />
- <PackageReference Include="System.Collections.Immutable" Version="5.0.0" />
- <PackageReference Include="System.ValueTuple" Version="4.5.0" />
+ 
+<PackageReference Condition="!'$(OldVersion)'" Include="System.Collections.Immutable" Version="6.0.0" />
+<PackageReference Condition="'$(OldVersion)'" Include="System.Collections.Immutable" Version="5.0.0" />
+<PackageReference Include="System.ValueTuple" Version="4.5.0" />
  </ItemGroup>
 
  <ItemGroup>