Bump NUnit from 4.5.1 to 4.6.0

---
updated-dependencies:
- dependency-name: NUnit
  dependency-version: 4.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

WellKnownDataTypes-Tests/WellKnownDataTypes-Tests.csproj

@@ -13,7 +13,7 @@
 
 	<ItemGroup>
 		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.5.1" />
-		<PackageReference Include="NUnit" Version="4.5.1" />
+		<PackageReference Include="NUnit" Version="4.6.0" />
 		<PackageReference Include="NUnit.Analyzers" Version="4.13.0">
 			<PrivateAssets>all</PrivateAssets>
 			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>