Bump pghero from 2.7.3 to 2.7.4 (#15668)

Bumps [pghero](https://github.com/ankane/pghero) from 2.7.3 to 2.7.4.
- [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/v2.7.3...v2.7.4)

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

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

Gemfile.lock

@@ -275,7 +275,7 @@ GEM
     httplog (1.4.3)
       rack (>= 1.0)
       rainbow (>= 2.0.0)
-    i18n (1.8.7)
+    i18n (1.8.8)
       concurrent-ruby (~> 1.0)
     i18n-tasks (0.9.33)
       activesupport (>= 4.0.2)
@@ -408,7 +408,7 @@ GEM
     pastel (0.8.0)
       tty-color (~> 0.5)
     pg (1.2.3)
-    pghero (2.7.3)
+    pghero (2.7.4)
       activerecord (>= 5)
     pkg-config (1.4.4)
     pluck_each (0.1.3)