Bump pg from 1.4.3 to 1.5.7 in /src/supermarket

Bumps [pg](https://github.com/ged/ruby-pg) from 1.4.3 to 1.5.7.
- [Changelog](https://github.com/ged/ruby-pg/blob/master/History.md)
- [Commits](ged/ruby-pg@v1.4.3...v1.5.7)

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

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

src/supermarket/Gemfile.lock

@@ -507,7 +507,7 @@ GEM
     parslet (1.8.2)
     pastel (0.8.0)
       tty-color (~> 0.5)
-    pg (1.4.3)
+    pg (1.5.7)
     pg_search (2.3.6)
       activerecord (>= 5.2)
       activesupport (>= 5.2)