[keyserver] Update mysql2 to 2.3.3
Summary: Depends on D4530
Test Plan:
- I ran the web application and clicked around a bunch. Full test plan will come later
- Checked mysql2 release notes to make sure there weren't any breaking changes or regressions
Reviewers: jonringer-comm, atul, palys-swm
Reviewed By: atul
Subscribers: Adrian, yayabosh
Differential Revision: https://phab.comm.dev/D4531