CI: bump macos-12 to 15

actions/runner-images#10721

Author: botovq

.github/workflows/macos.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: ["macos-14", "macos-13", "macos-12"]
+        os: ["macos-15", "macos-14", "macos-13"]
         arch: ["arm64", "x86_64"]
     steps:
     - name: "Install required packages"