[yarn] Bump buffer-util and utf-8-validate

Summary: The latest version of these packages have pre-built Apple Silicon binaries which resolves issues around building w/ node-gyp (that come up when bumping other dependencies).

Test Plan:
Apple Silicon: Ran y cleaninstall
Intel: If the CI catches any issues we can address them as they come up

Reviewers: varun, palys-swm, def-au1t, ashoat

Reviewed By: varun, ashoat

Subscribers: ashoat, Adrian, karol-bisztyga, boristopalov

Differential Revision: https://phabricator.ashoat.com/D2710