Use macos-11 in gha

Author: jneira

.github/workflows/test.yml

@@ -10,7 +10,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [macos-latest, ubuntu-latest, windows-latest]
+        os: [macos-11, ubuntu-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout