upgrade to macOS-15 in CI jobs

Author: deminy

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
     strategy:
       matrix:
         version: ["7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3", "8.4"]
-    runs-on: macos-12
+    runs-on: macos-15
     steps:
       - name: Checkout php-bsdiff
         uses: actions/checkout@v4