Bump pg from 1.5.5 to 1.5.6

Bumps [pg](https://github.com/ged/ruby-pg) from 1.5.5 to 1.5.6.
- [Changelog](https://github.com/ged/ruby-pg/blob/master/History.md)
- [Commits](ged/ruby-pg@v1.5.5...v1.5.6)

---
updated-dependencies:
- dependency-name: pg
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -542,7 +542,7 @@ GEM
       ast (~> 2.4.1)
       racc
     parslet (2.0.0)
-    pg (1.5.5)
+    pg (1.5.6)
     plek (5.0.0)
     prometheus_exporter (2.1.0)
       webrick