Revert attempt to move to .NET 5 TFM and use .NET Core 3.1 + PackageReference for UI Tests

Opened Issue microsoft/testfx#750

Author: michael-hawker

UITests/UITests.Tests.MSTest/UITests.Tests.MSTest.csproj

@@ -3,7 +3,7 @@
 
   <PropertyGroup>
 
-    <TargetFramework>net5.0-windows10.0.19041.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <TargetFrameworkIdentifier>.NETCoreApp</TargetFrameworkIdentifier>
     <TargetFrameworkVersion>v3.1</TargetFrameworkVersion>
     <RuntimeIdentifier>win10-x86</RuntimeIdentifier>
@@ -18,6 +18,10 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Condition="'$(TargetFramework)' == 'netcoreapp3.1'"
+                  Include="Microsoft.Windows.SDK.Contracts"
+                  Version="10.0.19041.0" />
+
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.7.1" />
     <PackageReference Include="MUXTestInfra.MSTest" Version="0.0.4" />
     <PackageReference Include="MSTest.TestAdapter" Version="2.1.2" />

UITests/UITests.Tests.TAEF/UITests.Tests.TAEF.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
 
-    <TargetFramework>net5.0-windows10.0.19041.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <TargetFrameworkIdentifier>.NETCoreApp</TargetFrameworkIdentifier>
     <TargetFrameworkVersion>v3.1</TargetFrameworkVersion>
     <LangVersion>8.0</LangVersion>
@@ -39,6 +39,10 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Condition="'$(TargetFramework)' == 'netcoreapp3.1'"
+                      Include="Microsoft.Windows.SDK.Contracts"
+                      Version="10.0.19041.0" />
+    
     <PackageReference Include="MUXTestInfra.TAEF" Version="0.0.4" />
     <PackageReference Include="TAEF.Redist.Wlk" Version="10.31.180822002" GeneratePathProperty="true" />
     <PackageReference Include="MUXCustomBuildTasks" Version="1.0.67" GeneratePathProperty="true" />