perf: Speedup one JSON unmarshal (backport #8398)

[mergify]

Speedup one JSON unmarshal being hit in production codepath

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This is an automatic backport of pull request #8398 done by Mergify.

[mergify]

Cherry-pick of 837b58c has failed:

On branch mergify/bp/v25.x/pr-8398
Your branch is up to date with 'origin/v25.x'.

You are currently cherry-picking commit 837b58c3.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   CHANGELOG.md

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   x/ibc-rate-limit/ibc_module.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[czarcas7ic]

@ValarDragon I don't think e2e is happy with this change on v25.x, I have run it a few times now