dev: Update glock

Created by: efritz

Upgrade efritz/glock, has migrated some time ago to derision-test/glock. I've patched the behavior of the new library to allow BlockingAdvance calls on ticker instances (not just the root clock), which allows us to have better control over advancing time in tests.

Incidentally, fixes https://github.com/sourcegraph/sourcegraph/issues/19127.