ci: use dotnet 9

Author: cnblogs-dudu

.github/workflows/ci.yml

@@ -22,11 +22,11 @@ jobs:
     name: ${{ matrix.runs-on }}
     runs-on: ${{ matrix.runs-on }}
     steps: 
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Setup .NET
       uses: actions/setup-dotnet@v2
       with:
-        dotnet-version: 7.0.x
+        dotnet-version: '9'
     - if: contains(matrix.runs-on, 'macOS') || contains(matrix.runs-on, 'ubuntu')
       env:
         MINVERVERSIONOVERRIDE: ${{ secrets.MINVER_VERSION }}