feat!: remove system config override feature

Author: schneider-felix

src/Components/SystemConfig/ConfigSystemConfigLoader.php

@@ -24,10 +24,6 @@ public function getConfigTreeBuilder(): TreeBuilder
                         ->end()
                     ->end()
                 ->end()
-                ->arrayNode('system_config')
-                    ->variablePrototype()
-                    ->end()
-                ->end()
             ->end()
         ;