Use the correct parameter variables in the hook docs for `wp_upgrade`.

See #27700.


git-svn-id: https://develop.svn.wordpress.org/trunk@27998 602fd350-edb4-49c9-b593-d223f7449a82
Don't try to resolve symlinks for single-file plugins. plugins_url() should not be used in this context anyway.

props rmccue.
fixes #16953.


git-svn-id: https://develop.svn.wordpress.org/trunk@27999 602fd350-edb4-49c9-b593-d223f7449a82
Use suggested language conventions in the hook docs description for the `theme_page_templates` filter.

See #27700.


git-svn-id: https://develop.svn.wordpress.org/trunk@28000 602fd350-edb4-49c9-b593-d223f7449a82