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

@@ -249,7 +249,7 @@ GEM
       actionmailer (>= 3, < 6)
       premailer (~> 1.7, >= 1.7.9)
     progress (3.5.0)
-    puma (3.12.2)
+    puma (3.12.6)
     rack (2.0.7)
     rack-accept (0.4.5)
       rack (>= 0.4)