Bump Microsoft.TestPlatform.ObjectModel from 16.8.0 to 16.8.3

Bumps [Microsoft.TestPlatform.ObjectModel](https://github.com/microsoft/vstest) from 16.8.0 to 16.8.3.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Commits](microsoft/vstest@v16.8.0...v16.8.3)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

src/xunit.runner.visualstudio/xunit.runner.visualstudio.csproj

@@ -34,7 +34,7 @@
 
   <ItemGroup>
     <PackageReference Include="xunit.runner.reporters" Version="$(XunitVersion)" PrivateAssets="All" />    
-    <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="16.8.0" PrivateAssets="All" />
+    <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="16.8.3" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup Label="Package">

test/test.xunit.runner.visualstudio/test.xunit.runner.visualstudio.csproj

@@ -12,7 +12,7 @@
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net46' ">
-    <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="16.8.0" />
+    <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="16.8.3" />
   </ItemGroup>
 
   <ItemGroup>