Make $taxonomy optional in get_term_link()

[scribu]

When get_term_link() receives an object as the first argument, it shouldn't require the second $taxonomy argument, since the $term object already has it.

if !is_object($term) we would need to then return WP_Error if we don't get a $taxonomy either.

Replying to nacin:

if !is_object($term) we would need to then return WP_Error if we don't get a $taxonomy either.

We would get a WP_Error from get_term() or get_term_by() so it's taken care of.

Patch still applies clean.

Related: #14156

(In [15586]) Make the second (taxonomy) parameter for get_term_link() optional if you pass in a term object as the first argument (which has the taxonomy in it). fixes #13081. props scribu