Updat tt() calls

update function calls for tt()

src/Core/L10n.php

@@ -174,7 +174,7 @@ class L10n
 	 * @param int $count
 	 * @return string
 	 */
-	function tt($singular, $plural, $count)
+	public static function tt($singular, $plural, $count)
 	{
 		global $lang;
 		$a = get_app();

src/Core/UserImport.php

@@ -231,7 +231,7 @@ class UserImport
 			}
 		}
 		if ($errorcount > 0) {
-			notice(sprintf(tt("%d contact not imported", "%d contacts not imported", $errorcount), $errorcount));
+			notice(sprintf(L10n::tt("%d contact not imported", "%d contacts not imported", $errorcount), $errorcount));
 		}
 
 		foreach ($account['group'] as &$group) {