[ci] Update macosx worker list

Supported github workers are now 14, 15 and 15-intel. 13 is deprecated.

Author: serge-sans-paille

.github/workflows/macos.yml

@@ -8,8 +8,9 @@ jobs:
     strategy:
       matrix:
         os:
-          - 13
           - 14
+          - 15
+          - 15-intel
     runs-on: macos-${{ matrix.os }}
     name: 'macos-${{ matrix.os }}'
     steps: