Bump NSubstitute from 5.3.0 to 6.0.0

---
updated-dependencies:
- dependency-name: NSubstitute
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

src/Directory.Packages.props

@@ -8,7 +8,7 @@
         <PackageVersion Include="Newtonsoft.Json" Version="13.0.4"/>
         <!--- Testing -->
         <PackageVersion Include="Microsoft.Testing.Extensions.CodeCoverage" Version="18.6.2"/>
-        <PackageVersion Include="NSubstitute" Version="5.3.0"/>
+        <PackageVersion Include="NSubstitute" Version="6.0.0"/>
         <PackageVersion Include="xunit.v3.mtp-v2" Version="3.2.2"/>
     </ItemGroup>