Bump NUnit.Engine.Api from 3.18.3 to 3.20.1

---
updated-dependencies:
- dependency-name: NUnit.Engine.Api
  dependency-version: 3.20.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

src/TestEngine/testcentric.engine/testcentric.engine.csproj

@@ -45,7 +45,7 @@
 
 	<ItemGroup>
 		<PackageReference Include="TestCentric.Engine.Api" Version="2.0.0-beta7" />
-		<PackageReference Include ="NUnit.Engine.Api" Version="3.18.3.0" />
+		<PackageReference Include="NUnit.Engine.Api" Version="3.20.1" />
 		<PackageReference Include="TestCentric.Extensibility" Version="3.1.0" />
 		<PackageReference Include="TestCentric.Metadata" Version="3.0.4" />
 		<PackageReference Include="TestCentric.InternalTrace" Version="1.2.1" />