Revert "Put Razor.Design.Test and Razor.Language.Test in a different test group (#6725)" (#6753)

This reverts commit 563ff7c.

Author: ajaybhargavb

src/Razor/Razor.Design/test/IntegrationTests/Microsoft.AspNetCore.Razor.Design.Test.csproj

@@ -13,7 +13,6 @@
     <!-- Copy references locally so that we can use them in the test. -->
     <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
     <BuildVariablesGeneratedFile>$(MSBuildProjectDirectory)\obj\BuildVariables.generated.cs</BuildVariablesGeneratedFile>
-    <TestGroupName>RazorTests</TestGroupName>
   </PropertyGroup>
 
   <ItemGroup>

src/Razor/Razor.Language/test/Microsoft.AspNetCore.Razor.Language.Test.csproj

@@ -4,7 +4,6 @@
     <TargetFrameworks>netcoreapp2.1;net46</TargetFrameworks>
     <DefaultItemExcludes>$(DefaultItemExcludes);TestFiles\**\*</DefaultItemExcludes>
     <DefineConstants Condition="'$(GenerateBaselines)'=='true'">$(DefineConstants);GENERATE_BASELINES</DefineConstants>
-    <TestGroupName>RazorTests</TestGroupName>
   </PropertyGroup>
 
   <ItemGroup>