update phpUnit to 8.1

Server is using 8.1 according to sysadmin. skipping 7.* tests

Signed-off-by: Rello <[email protected]>

Author: Rello

.github/workflows/phpunit.yml

@@ -16,7 +16,7 @@ jobs:
       # do not stop on another job's failure
       fail-fast: false
       matrix:
-        php-versions: ['7.2', '7.4', '8.0']
+        php-versions: ['8.1']
 
     name: php${{ matrix.php-versions }}