build(deps-dev): bump pg from 1.5.9 to 1.6.0

Bumps [pg](https://github.com/ged/ruby-pg) from 1.5.9 to 1.6.0.
- [Changelog](https://github.com/ged/ruby-pg/blob/master/CHANGELOG.md)
- [Commits](ged/ruby-pg@v1.5.9...v1.6.0)

---
updated-dependencies:
- dependency-name: pg
  dependency-version: 1.6.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -366,7 +366,9 @@ GEM
     parser (3.3.8.0)
       ast (~> 2.4.1)
       racc
-    pg (1.5.9)
+    pg (1.6.0)
+    pg (1.6.0-x86_64-darwin)
+    pg (1.6.0-x86_64-linux)
     pp (0.6.2)
       prettyprint
     prettyprint (0.2.0)