Bump NUnit.Analyzers from 4.5.0 to 4.6.0 in /UnitTests

Bumps [NUnit.Analyzers](https://github.com/nunit/nunit.analyzers) from 4.5.0 to 4.6.0.
- [Release notes](https://github.com/nunit/nunit.analyzers/releases)
- [Changelog](https://github.com/nunit/nunit.analyzers/blob/master/CHANGES.md)
- [Commits](nunit/nunit.analyzers@4.5.0...4.6.0)

---
updated-dependencies:
- dependency-name: NUnit.Analyzers
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

UnitTests/UnitTests.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="nunit" Version="4.3.2" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.6.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
-    <PackageReference Include="NUnit.Analyzers" Version="4.5.0" PrivateAssets="All" />      
+    <PackageReference Include="NUnit.Analyzers" Version="4.6.0" PrivateAssets="All" />      
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\src\Microsoft.IO.RecyclableMemoryStream.csproj" />