Add link to current MW train blocker task
Summary: Use the very convenient new tool https://train-blockers.toolforge.org/ to link to current MW train blocker task from here.
Test Plan: Load the page, click the link.
Reviewers: bd808, MarcoAurelio
Reviewed By: MarcoAurelio
Subscribers: MarcoAurelio
Tags: Deployments
Revert Plan: JFDI
Differential Revision: https://phabricator.wikimedia.org/D1183