SQL error preventing wp_signups table from being created on network install

[gradyetc]

Recent schema changes to the $ms_global_tables variable within /wp-admin/includes/schema.php are causing database errors when installing a network. The CREATE TABLE block for $wpdb->singups contains invalid SQL.

The resulting error:

WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'KEY user_login_email (user_login,user_email),\n  KEY domain_path (domain,path),\n)' at line 16 for query \nCREATE TABLE wp_signups (\n  signup_id bigint(20) NOT NULL auto_increment,\n  domain varchar(200) NOT NULL default '',\n  path varchar(100) NOT NULL default '',\n  title longtext NOT NULL,\n  user_login varchar(60) NOT NULL default '',\n  user_email varchar(100) NOT NULL default '',\n  registered datetime NOT NULL default '0000-00-00 00:00:00',\n  activated datetime NOT NULL default '0000-00-00 00:00:00',\n  active tinyint(1) NOT NULL default '0',\n  activation_key varchar(50) NOT NULL default '',\n  meta longtext,\n  PRIMARY KEY  (signup_id),\n  KEY activation_key (activation_key),\n  KEY user_email (user_email)\n  KEY user_login_email (user_login,user_email),\n  KEY domain_path (domain,path),\n) DEFAULT CHARACTER SET utf8 made by install_network, dbDelta

This error was introduced in [25179]. I've attached a patch against 25338.

[nacin]

In 25413:

Fix comma placement in [25179].

props gradyetc.
see #15004, fixes #25298.