Bump follow-redirects and @slack/bolt

Bumps [follow-redirects](https://github.com/follow-redirects/follow-redirects) to 1.15.2 and updates ancestor dependency [@slack/bolt](https://github.com/slackapi/bolt). These dependencies need to be updated together.


Updates `follow-redirects` from 1.5.10 to 1.15.2
- [Release notes](https://github.com/follow-redirects/follow-redirects/releases)
- [Commits](follow-redirects/follow-redirects@v1.5.10...v1.15.2)

Updates `@slack/bolt` from 2.1.1 to 2.7.0
- [Release notes](https://github.com/slackapi/bolt/releases)
- [Commits](https://github.com/slackapi/bolt/compare/@slack/[email protected]...@slack/[email protected])

---
updated-dependencies:
- dependency-name: follow-redirects
  dependency-type: indirect
- dependency-name: "@slack/bolt"
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]