Bump slack-bolt from 1.21.2 to 1.21.3 (#121)

Bumps [slack-bolt](https://github.com/slackapi/bolt-python) from 1.21.2 to 1.21.3.
- [Release notes](https://github.com/slackapi/bolt-python/releases)
- [Commits](slackapi/bolt-python@v1.21.2...v1.21.3)

---
updated-dependencies:
- dependency-name: slack-bolt
  dependency-type: direct:production
  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]

poetry.lock

@@ -49,7 +49,7 @@ email-validator = ">=1.3.0"         # Required by pydantic to validate emails us
 loguru = "^0.7.3"
 pydantic = ">=2.4.2"
 python = ">=3.11,<4"
-slack-bolt = "^1.18.1"
+slack-bolt = "^1.21.3"
 tornado = ">=6.4.2"