[server] Update to Node 15.3.0
Summary:
Announcement: https://nodejs.medium.com/node-js-v15-0-0-is-here-deb00750f278
Changelog: https://github.com/nodejs/node/blob/master/doc/changelogs/CHANGELOG_V15.md#15.3.0
Test Plan:
- I skimmed through the changelog and looked for anything that would affect us
- I made sure the website still loads and work
Reviewers: palys-swm
Reviewed By: palys-swm
Subscribers: KatPo, zrebcu411, Adrian
Differential Revision: https://phabricator.ashoat.com/D488