!chore: Bump CometBFT to v0.38.20 (backport #3929)

[mergify]

Description

• Bump CometBFT from v0.38.19 to v0.38.20

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Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• Included the correct type prefix in the PR title
• Added ! to the type prefix if API, client, or state breaking change (i.e., requires minor or major version bump)
• Targeted the correct branch (see PR Targeting)
• Provided a link to the relevant issue or specification
• Followed the guidelines for building SDK modules
• Included the necessary unit and integration tests
• Added a changelog entry in .changelog (for details, see contributing guidelines)
• Included comments for documenting Go code
• Updated the relevant documentation or specification
• Reviewed "Files changed" and left comments if necessary
• Confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage

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This is an automatic backport of pull request #3929 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 6a166e0 has failed:

On branch mergify/bp/release/v25.x/pr-3929
Your branch is up to date with 'origin/release/v25.x'.

You are currently cherry-picking commit 6a166e0.
  (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:   go.mod
	modified:   go.sum

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md
	both modified:   tests/interchain/go.mod
	both modified:   tests/interchain/go.sum

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