Update replies count for promoted sidebars

Test Plan: Check if replies count is increased after sending replies in promoted sidebars. Run the script and check if for promoted sidebars number of replies changed, checked if it's correct for some threads

Reviewers: ashoat, palys-swm

Reviewed By: ashoat, palys-swm

Subscribers: zrebcu411, Adrian, atul, subnub, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D715