Update grumphp configuration

Author: magicsunday

grumphp.yml

@@ -16,19 +16,22 @@ grumphp:
         phpstan:
             configuration: phpstan.neon
             memory_limit: '-1'
-            triggered_by: [ 'php' ]
+            triggered_by:
+                - php
             metadata:
                 priority: 600
         phpcs:
             metadata:
                 priority: 500
-            standard: ./vendor/squizlabs/php_codesniffer/src/Standards/PSR12/ruleset.xml
+            standard:
+                - PSR12
             severity: ~
             error_severity: ~
-            warning_severity: 9
+            warning_severity: ~
             tab_width: ~
             whitelist_patterns: []
             encoding: ~
             ignore_patterns: []
             sniffs: []
-            triggered_by: [ 'php' ]
+            triggered_by:
+                - php