[Treewide] Update h2 crate

Summary:
h2 v3.15 has a DoS vulnerability. This updates those crates.
h2 is used by tonic to serve the http2 grpc endpoint.

Test Plan: gates pass

Reviewers: ashoat, atul, varun, bartek, tomek

Reviewed By: atul

Differential Revision: https://phab.comm.dev/D7432