Bump pg from 1.4.5 to 1.4.6 in /backend

Bumps [pg](https://github.com/ged/ruby-pg) from 1.4.5 to 1.4.6.
- [Release notes](https://github.com/ged/ruby-pg/releases)
- [Changelog](https://github.com/ged/ruby-pg/blob/master/History.md)
- [Commits](ged/ruby-pg@v1.4.5...v1.4.6)

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

Signed-off-by: dependabot[bot] <support@github.com>

backend/Gemfile.lock

@@ -197,7 +197,7 @@ GEM
     nokogiri (1.14.2-x86_64-linux)
       racc (~> 1.4)
     os (1.1.4)
-    pg (1.4.5)
+    pg (1.4.6)
     public_suffix (5.0.1)
     puma (6.1.0)
       nio4r (~> 2.0)