fix: mysql (without the "i") class returned to its original state

this got replaced by all those mysql-to-mysqli find and replace
mumbo-jumbo tricks :)

install/process.php

@@ -124,7 +124,7 @@ class Process {
 		if(DB_TYPE) {
 			$result = $database->connection->multi_query($str);
 		} else {
-			$result = $database->mysqli_exec_batch($str);
+			$result = $database->mysql_exec_batch($str);
 		}
 		if($result) {
 			header("Location: index.php?s=3");