ci: remove macos-13 (deprecated Intel runner)

Author: hueifeng

.github/workflows/dotnetcore.yml

@@ -18,7 +18,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-22.04, ubuntu-latest, windows-latest, macos-13, macos-latest]
+        os: [ubuntu-22.04, ubuntu-latest, windows-latest, macos-latest]
 
     steps:
       - uses: actions/checkout@v4