Bump puma from 4.1.0 to 4.2.1

Bumps [puma](https://github.com/puma/puma) from 4.1.0 to 4.2.1.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v4.1.0...v4.2.1)

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

Gemfile.lock

@@ -207,7 +207,7 @@ GEM
     multi_xml (0.6.0)
     multipart-post (2.1.1)
     netrc (0.11.0)
-    nio4r (2.4.0)
+    nio4r (2.5.2)
     nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     oauth (0.5.4)
@@ -241,7 +241,7 @@ GEM
     pghero (2.3.0)
       activerecord (>= 5)
     public_suffix (3.1.1)
-    puma (4.1.0)
+    puma (4.2.1)
       nio4r (~> 2.0)
     rack (2.0.7)
     rack-accept-default (0.0.2)