Convert various uses of (optional) in core parameter descriptions to use the style prescribed in the inline documentation standards for PHP.

The style for marking parameters optional in inline PHP docs is: `@param type $var Optional. Description. Accepts. Default.`, where Accepts can be omitted on a case-by-case basis.

Props coffee2code.
Fixes #30591.

Built from https://develop.svn.wordpress.org/trunk@30753


git-svn-id: http://core.svn.wordpress.org/trunk@30743 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/wp-db.php

@@ -735,8 +735,8 @@ class wpdb {
 	 * @since 3.1.0
 	 *
 	 * @param resource $dbh     The resource given by mysql_connect
-	 * @param string   $charset The character set (optional)
-	 * @param string   $collate The collation (optional)
+	 * @param string   $charset Optional. The character set. Default null.
+	 * @param string   $collate Optional. The collation. Default null.
 	 */
 	public function set_charset( $dbh, $charset = null, $collate = null ) {
 		if ( ! isset( $charset ) )