Upgrade tonic to v0.12.3 to fix security vulnerability

[boxofrad]

What was changed

cd temporalio/bridge && cargo update tonic --precise 0.12.3

Why?

Pulls in fix for CVE-2024-47609, which has started showing up in our container scanner reports.

[CLAassistant]

All committers have signed the CLA.

[cretz]

Thanks! Will merge if/when CI passes (there are a couple of other things in 0.12.2+ that were fixed wrt TLS using system certs too IIUC). EDIT: There are some flakes in CI currently, but nothing specific to your change, we should be able to merge shortly.