Add support for `wp_remove_object_terms()`

[ericmann]

WordPress currently provides functions for setting and retrieving taxonomy terms for a post, but there is no support for removing taxonomy terms. Currently, developers must:

1. Get an array of terms for an object
2. Remove selected terms from the array
3. Overwrite the object's terms using wp_set_object_terms()

This process is somewhat standard, and not too difficult to manage. But most other functions in core come in a get/set/delete set, and this should be no exception.

wp_remove_object_terms() should accept similar parameters as wp_set_object_terms().

[trepmal]

wp_remove_object_terms()

[trepmal]

Function is based significantly off wp_set_object_terms()

[nacin]

Duplicate of #15475, methinks.

[ericmann]

Replying to nacin:

Duplicate of #15475, methinks.

Methinks you're right. Sadly, that one didn't turn up in my search when I looked first time 'round.