Bump slack-sdk from 3.27.2 to 3.29.0 (#4829)

Bumps [slack-sdk](https://github.com/slackapi/python-slack-sdk) from 3.27.2 to 3.29.0.
- [Release notes](https://github.com/slackapi/python-slack-sdk/releases)
- [Changelog](https://github.com/slackapi/python-slack-sdk/blob/main/docs-v2/changelog.html)
- [Commits](slackapi/python-slack-sdk@v3.27.2...v3.29.0)

---
updated-dependencies:
- dependency-name: slack-sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements-base.txt

@@ -396,7 +396,7 @@ six==1.16.0
     #   validators
 slack-bolt==1.18.1
     # via -r requirements-base.in
-slack-sdk==3.27.2
+slack-sdk==3.29.0
     # via
     #   -r requirements-base.in
     #   slack-bolt