ci: don't use mac runner

Author: chu-k

.github/workflows/main.yml

@@ -15,7 +15,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-14]
+        os: [ubuntu-latest]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout