Bump NUnit from 3.13.3 to 3.14.0 (#200)

Bumps [NUnit](https://github.com/nunit/nunit) from 3.13.3 to 3.14.0.
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/master/CHANGES.md)
- [Commits](nunit/nunit@v3.13.3...v3.14.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

SharpXMPP.NUnit/SharpXMPP.NUnit.csproj

@@ -18,7 +18,7 @@
   <ItemGroup>
     <PackageReference Include="JetBrains.DotMemoryUnit" Version="3.2.20220510" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
-    <PackageReference Include="NUnit" Version="3.13.3" />
+    <PackageReference Include="NUnit" Version="3.14.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
   </ItemGroup>