CI: Modify os name

Author: ichizok

.github/workflows/ci-macvim.yaml

@@ -33,15 +33,15 @@ jobs:
   # Builds and test MacVim
   build-and-test:
 
-    # Test on macOS 10.15 / 11.0, and also older version of Xcode for compatibility testing.
+    # Test on macOS 10.15 / 11.x, and also older version of Xcode for compatibility testing.
     strategy:
       fail-fast: false
       matrix:
         include:
           - os: macos-10.15
             xcode: 11.7
           - os: macos-10.15
-          - os: macos-11.0
+          - os: macos-11
             publish: true
 
     runs-on: ${{ matrix.os }}