chore: Fix default PHP version (#27)

Author: keelerm84

.github/actions/ci/action.yml

@@ -4,7 +4,7 @@ inputs:
   php-version:
     description: 'Which version of PHP should we setup?'
     required: false
-    default: 7.4
+    default: 8.1
   use-lowest-dependencies:
     description: 'Should we prefer the lowest dependency version?'
     type: boolean