Add inline documentation for default arguments in `wp_insert_category()`.

See #28298.

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git-svn-id: http://core.svn.wordpress.org/trunk@28301 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix wp_insert_link(), broken in [28406]/[28408].

see #22400.
Built from https://develop.svn.wordpress.org/trunk@28475


git-svn-id: http://core.svn.wordpress.org/trunk@28302 1a063a9b-81f0-0310-95a4-ce76da25c4cd