Bump pg from 1.2.3 to 1.3.4 in /backend

Bumps [pg](https://github.com/ged/ruby-pg) from 1.2.3 to 1.3.4.
- [Release notes](https://github.com/ged/ruby-pg/releases)
- [Changelog](https://github.com/ged/ruby-pg/blob/master/History.rdoc)
- [Commits](ged/ruby-pg@v1.2.3...v1.3.4)

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

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

Author: dependabot[bot]

backend/Gemfile.lock

@@ -107,7 +107,7 @@ GEM
     nokogiri (1.12.5)
       mini_portile2 (~> 2.6.1)
       racc (~> 1.4)
-    pg (1.2.3)
+    pg (1.3.4)
     public_suffix (4.0.6)
     puma (5.5.2)
       nio4r (~> 2.0)