Use reduced test matrix on MacOSX

Since there's a Mojolicious dependency, the minimal version that is to be
supported is 5.16.

Co-authored-by: @perlpunk <tina.mueller@suse.com>

Author: foursixnine

.github/workflows/ci-linux.yaml

@@ -11,11 +11,16 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: ['ubuntu-latest','macos-latest']
-        perl: 
+      os: [ubuntu-latest]
+        perl:
+          - '5.16'
+          - '5.20'
           - '5.26'
           - '5.30'
-          - 'latest'
+          - latest
+        include:
+          - { os: macos-latest, perl: '5.26' }
+          - { os: macos-latest, perl: latest }
     name: 🐪 Perl ${{ matrix.perl }} on ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2