remove unneeded LOWER. Fixes #8202

lib/private/user/database.php

@@ -121,7 +121,7 @@ class OC_User_Database extends OC_User_Backend {
 	 */
 	public function setDisplayName($uid, $displayName) {
 		if ($this->userExists($uid)) {
-			$query = OC_DB::prepare('UPDATE `*PREFIX*users` SET `displayname` = ? WHERE LOWER(`uid`) = ?');
+			$query = OC_DB::prepare('UPDATE `*PREFIX*users` SET `displayname` = ? WHERE LOWER(`uid`) = LOWER(?)');
 			$query->execute(array($displayName, $uid));
 			return true;
 		} else {