Remove macos-11 from build matrix

It is pretty old.
GH seems to have issues finding a runner for it.

Author: g3force

.github/workflows/build.yaml

@@ -27,7 +27,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ macos-11, macos-12, macos-13 ]
+        os: [ macos-12, macos-13 ]
     steps:
       - uses: actions/checkout@v4
       - name: "Install dependencies"