[TASK] Switch the static analysis CI jobs to PHP 8.3 (MyIntervals#446)

This should improve CI performance a bit.

Author: oliverklee

.github/workflows/ci.yml

@@ -89,7 +89,7 @@ jobs:
           - fixer
           - stan
         php-version:
-          - '7.4'
+          - '8.3'
 
     steps:
       - name: Checkout