macos-10.15 image label should be updated to ... up to macOS-13 with intel

Author: jtulach

.github/workflows/mac.yml

@@ -32,7 +32,7 @@ jobs:
     strategy:
       matrix:
         java: [ '8', '11', '17', '21' ]
-        os: [ macos-10.15 ]
+        os: [ macos-13 ]
 
     steps:
     - uses: actions/checkout@v2