[Tests] Update PHP versions

Add 8.1 and remove 7.3

Author: hlecorche

.github/workflows/tests.yml

@@ -17,9 +17,9 @@ jobs:
                         composer-flags: '--prefer-stable --prefer-lowest'
                         description: 'with lowest'
                     -   php-version: '7.2'
-                    -   php-version: '7.3'
                     -   php-version: '7.4'
                     -   php-version: '8.0'
+                    -   php-version: '8.1'
                     -   php-version: '8.0'
                         description: 'with Coding Standards'
                         coding-standards: true