Broken link to kickoff doc in product handbook page
Description
First link to kickoff doc in the Product Process section is broken (markdown typo, see here).
Proposal
Fix it: ([Kickoff document](https://docs.google.com/document/d/1ElPkZ90A8ey_iOkTvUs_ByMlwKK6NAB2VOK5835wYK0/edit))
cc @gl-website