CI: Update macos images to macos-13

Author: ehuss

.github/workflows/main.yml

@@ -134,11 +134,11 @@ jobs:
           rust: nightly
           other: i686-unknown-linux-gnu
         - name: macOS x86_64 stable
-          os: macos-latest
+          os: macos-13
           rust: stable
           other: x86_64-apple-ios
         - name: macOS x86_64 nightly
-          os: macos-latest
+          os: macos-13
           rust: nightly
           other: x86_64-apple-ios
         - name: macOS aarch64 stable