Bump xunit from 2.8.0 to 2.9.0

Bumps xunit from 2.8.0 to 2.9.0.

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

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

test/stiebel-eltron-dashboard-tests.csproj

@@ -7,7 +7,7 @@
 	</PropertyGroup>
 	<ItemGroup>
 		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
-		<PackageReference Include="xunit" Version="2.8.0" />
+		<PackageReference Include="xunit" Version="2.9.0" />
 		<PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
 			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
 			<PrivateAssets>all</PrivateAssets>