ci: Bump GitHub actions to latest versions

Author: hangy

.github/workflows/ci.yml

@@ -22,9 +22,9 @@ jobs:
       contents: write
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Setup
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           global-json-file: global.json
       - name: Compute build number