Replaced macos-15-intel from macos-13 and added macos-15 (#198)

Author: hsbt

.github/workflows/macos.yml

@@ -19,8 +19,9 @@ jobs:
       fail-fast: false
       matrix:
         os:
-        - macos-13
         - macos-14
+        - macos-15-intel
+        - macos-15
         ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
     steps:
     - name: git config