Fixed a bug with delete_term_meta API (meta name was required)

[fembuelita]

Simple iterate over each field to delete each term individually.

[ocholabs]

Hi, if you do this fix you'll get php warnings as in
delete_term_meta( $term_id, $field );
$field is an array and you should pass a string
I changed it to
delete_term_meta( $term_id, $field['id']);
And got no more warnings now.