CI: bump to macOS 15 on x86_64

Author: TheTumultuousUnicornOfDarkness

.github/workflows/build_macos.yml

@@ -20,7 +20,7 @@ jobs:
       matrix:
         os:
           - { label: macos-15, name: macos-aarch64 }
-          - { label: macos-13, name: macos-x86_64 }
+          - { label: macos-15-intel, name: macos-x86_64 }
     env:
       OS_NAME: ${{ matrix.os.name }}