Upgrade macOS image to 12

macOS 12 on GHA is now GA: https://github.blog/changelog/2022-06-13-github-actions-macos-12-for-github-hosted-runners-is-now-generally-available/

Signed-off-by: Yuki Okushi <jtitor@2k36.org>

.github/workflows/bors.yml

@@ -29,7 +29,7 @@ jobs:
 
   macos:
     name: macOS
-    runs-on: macos-11
+    runs-on: macos-12
     strategy:
       fail-fast: true
       matrix:
@@ -223,7 +223,7 @@ jobs:
   build_channels_macos:
     name: Build Channels macOS
     needs: macos
-    runs-on: macos-11
+    runs-on: macos-12
     env:
       OS: macos
     strategy:
@@ -290,7 +290,7 @@ jobs:
   semver_macos:
     if: ${{ false }} # This is currently broken
     name: Semver macOS
-    runs-on: macos-11
+    runs-on: macos-12
     continue-on-error: true
     steps:
       - uses: actions/checkout@v3

.github/workflows/main.yml

@@ -27,7 +27,7 @@ jobs:
 
   macos:
     name: macOS
-    runs-on: macos-11
+    runs-on: macos-12
     strategy:
       fail-fast: true
       matrix: