update macOS-11 runners to macOS-13 (#370)

Author: DimitrisStaratzis

.github/workflows/github_actions.yml

@@ -154,7 +154,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ macos-11, ubuntu-latest, macos-14]
+        os: [ macos-13, ubuntu-latest, macos-14]
     steps:
 
       - name: Set up Java