Update macos.yml

Author: langonginc

.github/workflows/macos.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         os: [macos-10.15]
-        qt_ver: [5.9.9,5.12.10,5.15.2]
+        qt_ver: [5.15.2]
         qt_arch: [clang_64]
     env:
       targetName: QMineSweeper