Update run-tests.yml

Author: patinthehat

.github/workflows/run-tests.yml

@@ -13,7 +13,7 @@ jobs:
       fail-fast: true
       matrix:
         os: [ubuntu-latest]
-        php: [7.3, 7.4, 8.0, 8.1, 8.2]
+        php: [7.3, 7.4, 8.0, 8.1, 8.2, 8.3]
         stability: [prefer-stable]
 
     name: P${{ matrix.php }} - ${{ matrix.stability }} - ${{ matrix.os }}