Bump pghero from 2.1.1 to 2.2.0

Bumps [pghero](https://github.com/ankane/pghero) from 2.1.1 to 2.2.0.
- [Release notes](https://github.com/ankane/pghero/releases)
- [Changelog](https://github.com/ankane/pghero/blob/master/CHANGELOG.md)
- [Commits](ankane/pghero@v2.1.1...v2.2.0)

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

Gemfile.lock

@@ -221,7 +221,7 @@ GEM
       rack
     pg (1.0.0)
     pg_query (1.0.2)
-    pghero (2.1.1)
+    pghero (2.2.0)
       activerecord
     public_suffix (3.0.3)
     puma (3.12.0)