Bump puma from 3.12.2 to 3.12.6

Bumps [puma](https://github.com/puma/puma) from 3.12.2 to 3.12.6.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](https://github.com/puma/puma/commits)

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

Gemfile.lock

@@ -229,7 +229,7 @@ GEM
       slop (~> 3.4)
     pry-rails (0.3.2)
       pry (>= 0.9.10)
-    puma (3.12.2)
+    puma (3.12.6)
     pundit (0.3.0)
       activesupport (>= 3.0.0)
     quiet_assets (1.0.3)