Ensure the private function `_wp_render_title_tag()` is marked for internal usage only.

See #30469.

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git-svn-id: http://core.svn.wordpress.org/trunk@30605 1a063a9b-81f0-0310-95a4-ce76da25c4cd
4.1 Docs Audit: Ensure optional arguments in `get_the_post_navigation()`, `the_post_navigation()`, `get_the_posts_navigation()`, `the_posts_navigation()`, `get_the_pagination()`, and `the_pagination()` are properly documented with defaults.

See #30469.

Built from https://develop.svn.wordpress.org/trunk@30616


git-svn-id: http://core.svn.wordpress.org/trunk@30606 1a063a9b-81f0-0310-95a4-ce76da25c4cd