Bump pg from 1.4.6 to 1.5.9

Bumps [pg](https://github.com/ged/ruby-pg) from 1.4.6 to 1.5.9.
- [Changelog](https://github.com/ged/ruby-pg/blob/master/History.md)
- [Commits](ged/ruby-pg@v1.4.6...v1.5.9)

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

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

Gemfile.lock

@@ -203,7 +203,7 @@ GEM
     parallel (1.22.1)
     parser (3.2.1.1)
       ast (~> 2.4.1)
-    pg (1.4.6)
+    pg (1.5.9)
     protocol-hpack (1.4.2)
     protocol-http (0.25.0)
     protocol-http1 (0.16.1)