Fix mysql import in nextcloud readme (#2210)

nextcloud/content.md

@@ -496,7 +496,7 @@ You're already using Nextcloud and want to switch to docker? Great! Here are som
 
 	```console
 	docker cp ./database.dmp nextcloud_db_1:/dmp
-	docker-compose exec db sh -c "mysql -u USER -p PASSWORD nextcloud < /dmp"
+	docker-compose exec db sh -c "mysql --user USER --password PASSWORD nextcloud < /dmp"
 	docker-compose exec db rm /dmp
 	```