ci: replace eol mac runner with mac-12

Author: artis3n

.github/workflows/tests.yml

@@ -18,7 +18,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: ['macos-10.15', 'ubuntu-latest']
+        os: ['macos-12', 'ubuntu-latest']
     runs-on: ${{ matrix.os }}
 
     steps: