Ask Jenkins to use the main branch
Summary:
By default, Jenkins clones the master branch instead of main.
Ref T1668
Test Plan: https://cd.nasqueron.org/view/Static%20websites/job/deploy-website-nasqueron-www1-infra/22/console
Reviewers: dereckson
Reviewed By: dereckson
Maniphest Tasks: T1668
Differential Revision: https://devcentral.nasqueron.org/D2561