Remove duplicate code

Author: GromNaN

src/DependencyInjection/DoctrineMongoDBExtension.php

@@ -279,10 +279,6 @@ protected function registerMappingDrivers(array $objectManager, ContainerBuilder
                 }
 
                 $mappingDriverDef->setArguments($args);
-            } elseif ($driverType === 'attribute') {
-                $mappingDriverDef = new Definition($this->getMetadataDriverClass($driverType), [
-                    array_values($driverPaths),
-                ]);
             } else {
                 $mappingDriverDef = new Definition($this->getMetadataDriverClass($driverType), [
                     array_values($driverPaths),
@@ -326,7 +322,7 @@ protected function assertValidMappingConfiguration(
         }
 
         if (! in_array($mappingConfig['type'], ['xml', 'attribute'])) {
-            throw new InvalidArgumentException(sprintf('Can only configure  "xml" or "attribute" through the DoctrineMongoDBBundle. Use your own bundle to configure other metadata drivers. You can register them by adding a new driver to the "%s" service definition.', $this->getObjectManagerElementName($objectManagerName . '_metadata_driver')));
+            throw new InvalidArgumentException(sprintf('Can only configure "xml" or "attribute" through the DoctrineMongoDBBundle. Use your own bundle to configure other metadata drivers. You can register them by adding a new driver to the "%s" service definition.', $this->getObjectManagerElementName($objectManagerName . '_metadata_driver')));
         }
     }