#2906 - Set reviews count in tab to only count actual reviews

Nested comments shouldn’t be treated as reviews. This addresses that by
using `$product->get_rating_count()` to determine the correct number of
reviews, instead of get_comments_number.

It can be filtered using the new `woocommerce_product_reviews_count`
filter.
Remove previously added filter, not necessary
Merge pull request #6798 from bryceadams/patch-2906

#2906 - Set reviews count in tab to only count actual reviews