Bump pghero from 3.3.4 to 3.4.0

Bumps [pghero](https://github.com/ankane/pghero) from 3.3.4 to 3.4.0.
- [Changelog](https://github.com/ankane/pghero/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ankane/pghero/compare/v3.3.4...v3.4.0)

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

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

Gemfile.lock

@@ -294,7 +294,7 @@ GEM
       ast (~> 2.4.1)
       racc
     pg (1.5.4)
-    pghero (3.3.4)
+    pghero (3.4.0)
       activerecord (>= 6)
     prometheus-client (4.2.2)
     public_suffix (5.0.3)