Better description and fixed typo for `_WP_Editors::parse_settings()`.

See [27808]. See #27566.


git-svn-id: https://develop.svn.wordpress.org/trunk@27809 602fd350-edb4-49c9-b593-d223f7449a82
Wow. One more time with the typos.

I can, in fact, spell 'instance'.

See #27566.


git-svn-id: https://develop.svn.wordpress.org/trunk@27810 602fd350-edb4-49c9-b593-d223f7449a82