chore(deps-dev): bump boto3-stubs from 1.38.19 to 1.38.21 (#6698)

Bumps [boto3-stubs](https://github.com/youtype/mypy_boto3_builder) from 1.38.19 to 1.38.21.
- [Release notes](https://github.com/youtype/mypy_boto3_builder/releases)
- [Commits](https://github.com/youtype/mypy_boto3_builder/commits)

---
updated-dependencies:
- dependency-name: boto3-stubs
  dependency-version: 1.38.21
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]