…mint#3017) (tendermint#3026)

Minor speedup to metrics MarkLateVote.

I saw the excess string allocation calls, so made a quick PR to remove
it. This saves between .18s-25s from the consensus mutex across this one
hour block sync. (Likely not at all consensus critical) It also appears
in receiving votes


![image](https://github.com/cometbft/cometbft/assets/6440154/61875b0d-b419-4900-a74c-76c65087bca4)

(Saves ToLower(), .String(), .TrimPrefix() and newObject calls. The new
call has comparable complexity to .String())

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#### PR checklist

- [x] Tests written/updated
- [x] Changelog entry added in `.changelog` (we use
[unclog](https://github.com/informalsystems/unclog) to manage our
changelog)
- [x] Updated relevant documentation (`docs/` or `spec/`) and code
comments
- [x] Title follows the [Conventional
Commits](https://www.conventionalcommits.org/en/v1.0.0/) spec
<hr>This is an automatic backport of pull request tendermint#3017 done by
[Mergify](https://mergify.com).

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Co-authored-by: Dev Ojha <ValarDragon@users.noreply.github.com>
Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>