4.1 Docs Audit: Fix a variety of issues with the DocBlock for the `default_page_template_title` filter.

Includes hyphenating 'drop-down', ensuring the DocBlock itself is correctly indented, and wraps lines at an appropriate length.

See #30469.


git-svn-id: https://develop.svn.wordpress.org/trunk@30601 602fd350-edb4-49c9-b593-d223f7449a82