Media: Add `heic` extension to `wp_get_ext_types()`, for consistency with `wp_get_mime_types()`.

Follow-up to [48288].

Props imath.
Fixes #50557. See #42775.
Built from https://develop.svn.wordpress.org/trunk@48296


git-svn-id: https://core.svn.wordpress.org/trunk@48065 1a063a9b-81f0-0310-95a4-ce76da25c4cd