Bump puma from 3.12.3 to 3.12.4 (#548)

Bumps [puma](https://github.com/puma/puma) from 3.12.3 to 3.12.4.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.12.3...v3.12.4)

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

Gemfile.lock

@@ -508,7 +508,7 @@ GEM
     pry-rails (0.3.9)
       pry (>= 0.10.4)
     public_suffix (3.1.1)
-    puma (3.12.3)
+    puma (3.12.4)
     raabro (1.1.6)
     rack (2.0.8)
     rack-accept (0.4.5)