Bump pghero from 2.8.0 to 2.8.1 (#15962)

Bumps [pghero](https://github.com/ankane/pghero) from 2.8.0 to 2.8.1.
- [Release notes](https://github.com/ankane/pghero/releases)
- [Changelog](https://github.com/ankane/pghero/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ankane/pghero/compare/v2.8.0...v2.8.1)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -450,7 +450,7 @@ GEM
     pastel (0.8.0)
       tty-color (~> 0.5)
     pg (1.2.3)
-    pghero (2.8.0)
+    pghero (2.8.1)
       activerecord (>= 5)
     pkg-config (1.4.5)
     posix-spawn (0.3.15)