Update SDK version to 14.0 for Kubernetes 1.30 (#1551)

* Update KUBERNETES_BRANCH to v1.30.0 in csharp.settings

* Update version.json to 14.0

* Update SDK version to 14.0 for Kubernetes 1.30

* fix csharp naming conflict

* drop support of net7

* remove unused comment

.github/workflows/codeql-analysis.yml

@@ -29,9 +29,7 @@ jobs:
       uses: actions/setup-dotnet@v4
       with:
         dotnet-version: |
-          3.1.x
           6.0.x
-          7.0.x
           8.0.x
 
     # Initializes the CodeQL tools for scanning.