Bump follow-redirects in /cloud-functions/alerts-tiler

Bumps [follow-redirects](https://github.com/follow-redirects/follow-redirects) from 1.15.2 to 1.15.4.
- [Release notes](https://github.com/follow-redirects/follow-redirects/releases)
- [Commits](follow-redirects/follow-redirects@v1.15.2...v1.15.4)

---
updated-dependencies:
- dependency-name: follow-redirects
  dependency-type: indirect
...

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