Determines whether the current request is for a user admin screen.

e.g. `/wp-admin/user/`

Does not check if the user is an administrator; use current_user_can()
for checking roles and capabilities.

function is_user_admin() {
	if ( isset( $GLOBALS['current_screen'] ) ) {
		return $GLOBALS['current_screen']->in_admin( 'user' );
	} elseif ( defined( 'WP_USER_ADMIN' ) ) {
		return WP_USER_ADMIN;
	}

	return false;
}