GHA: Update CI to use os: macos-latest

Connects to <PDLPorters/devops#46>.

Author: zmughal

.github/workflows/ci.yml

@@ -34,7 +34,7 @@ jobs:
           #- perl-version: '5.30'
           #  os: windows-latest
           - perl-version: '5.30'
-            os: macos-11
+            os: macos-latest
     steps:
       - uses: actions/checkout@v2
       - name: 'ci-dist: target-setup-perl'