[UT-5995] Update protoc image to latest alpine and buf version

[BCook98]

Summary

Pulls in the latest buf version, and also updates alpine at the same time!

Problem description

Pros/cons of approach implemented

Checklist

• Is this PR a reasonable size?

• List deployment sequence with all relevant PRs.
  • ...

• For breaking changes: I have confirmed that other repos are not affected, or I have planned a deployment sequence to address any impact.

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[lachlancooper]

I tried a similar change in #151 but hit issues with several builds failing, and had to revert it in #154.

(The failures were not obvious in advance back then, so I introduced auto-triggered builds in #156).

FYI I also tried bumping buf in https://github.com/SafetyCulture/APISchema/pull/4684, which introduced a whole bunch of config and formatting changes. Not blocking, but it may take some work to fully roll this out.