Bump pg from 1.5.6 to 1.5.7 (#879)

Bumps [pg](https://github.com/ged/ruby-pg) from 1.5.6 to 1.5.7.
- [Changelog](https://github.com/ged/ruby-pg/blob/master/History.md)
- [Commits](ged/ruby-pg@v1.5.6...v1.5.7)

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

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

Gemfile.lock

@@ -298,7 +298,7 @@ GEM
     parser (3.3.4.0)
       ast (~> 2.4.1)
       racc
-    pg (1.5.6)
+    pg (1.5.7)
     protocol-hpack (1.4.3)
     protocol-http (0.26.4)
     protocol-http1 (0.19.0)