Docs: mistake in wp_insert_term inline documentation

[audrasjb]

There is a mistake in wp_insert_term inline docs:
The error is located here: https://core.trac.wordpress.org/browser/tags/5.4/src/wp-includes/taxonomy.php#L2103

"The term name to add or update."

Given terms can only be added and not updated, we should say "The term name to add".

Props should be attributed to @bmartinent who spotted the issue.

[audrasjb]

Fix inline docs

[SergeyBiryukov]

In 48600:

Docs: Correct documentation for wp_insert_term().

The function is used for adding a new term, not updating an existing one.

Props audrasjb, bmartinent.
Fixes #50753.