CI: Add fail-fast: false to get the whole picture

Author: amotl

.github/workflows/tests.yml

@@ -18,6 +18,7 @@ jobs:
   tests:
     runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
         os: [ ubuntu-latest ] # macos-latest, windows-latest
         ruby-version: [ "2.6", "2.7", "3.0", "3.1" ]