loosen patch versions in tests

Author: Floppy

.github/workflows/push.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['2.5.8']
+        ruby-version: ['2.5', '2.6', '2.7']
       fail-fast: false
     steps:
       - uses: actions/checkout@v2