Bump @slack/bolt from 3.21.1 to 3.21.4

Bumps [@slack/bolt](https://github.com/slackapi/bolt) from 3.21.1 to 3.21.4.
- [Release notes](https://github.com/slackapi/bolt/releases)
- [Commits](https://github.com/slackapi/bolt/compare/@slack/bolt@3.21.1...@slack/bolt@3.21.4)

---
updated-dependencies:
- dependency-name: "@slack/bolt"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -9,7 +9,7 @@
   },
   "dependencies": {
     "dotenv": "^16",
-    "@slack/bolt": "^3.21.1",
+    "@slack/bolt": "^3.21.4",
     "node-localstorage": "^3.0.5"
   },
   "engines": {