Fix typo in wp_insert_term() error strings

[SergeyBiryukov]

In [26544], two new strings were introduced:

• "A term with the name and slug provided already exists with this parent."
• "A term with the name and slug provided already exists."

In [30240], the "provided" word was lost somehow:

• "A term with the name and slug already exists with this parent."
• "A term with the name and slug already exists in this taxonomy."

In [31734], "and slug" was removed, but the "provided" is still missing:

• "A term with the name already exists with this parent."
• "A term with the name already exists in this taxonomy."

[dipesh.kakadiya]

Updated typo

[SergeyBiryukov]

In 32297:

Add missing word to wp_insert_term() error strings.

props dipesh.kakadiya.
fixes #32031.