CI: avoid cancelling all build steps if one fails

Author: orien

.github/workflows/test.yml

@@ -6,6 +6,7 @@ jobs:
     name: Test (Ruby ${{ matrix.ruby }}, ${{ matrix.os }})
     runs-on: ${{ matrix.os }}-latest
     strategy:
+      fail-fast: false
       matrix:
         os: [ ubuntu ]
         ruby: [ '2.4', '2.5', '2.6', '2.7', '3.0', '3.1', '3.2', '3.3', '3.4' ]