[skip ci] docs/release-process.md: Update a link to php 8.6 release schedule

Add the PHP 8.6 wiki TODO page to the release process schedule links.

Author: LamentXU123

docs/release-process.md

@@ -6,6 +6,7 @@ repository available according to the release schedule.
 The release schedule for each version is published on the
 [PHP wiki](https://wiki.php.net):
 
+- [PHP 8.6](https://wiki.php.net/todo/php86)
 - [PHP 8.5](https://wiki.php.net/todo/php85)
 - [PHP 8.4](https://wiki.php.net/todo/php84)
 - [PHP 8.3](https://wiki.php.net/todo/php83)