Use correct identifier for macOS runner in test workflows

The official GitHub Actions documentation specifies the hosted macOS runner names use the `macos` prefix. Although the
non-compliant case previously in use clearly does work, there is no guarantee it will continue to do so, so it's safest
to follow the documentation exactly.

Author: per1234

.github/workflows/test-go-integration-task.yml

@@ -39,7 +39,7 @@ jobs:
         operating-system:
           - ubuntu-latest
           - windows-latest
-          - macOS-latest
+          - macos-latest
 
     runs-on: ${{ matrix.operating-system }}
 

.github/workflows/test-go-task.yml

@@ -33,7 +33,7 @@ jobs:
         operating-system:
           - ubuntu-latest
           - windows-latest
-          - macOS-latest
+          - macos-latest
 
     runs-on: ${{ matrix.operating-system }}