Bump puma from 3.10.0 to 4.3.1

Bumps [puma](https://github.com/puma/puma) from 3.10.0 to 4.3.1.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.10.0...v4.3.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -112,6 +112,7 @@ GEM
     multi_test (0.1.2)
     mustermann (1.0.2)
     netrc (0.11.0)
+    nio4r (2.3.1)
     nokogiri (1.8.2)
       mini_portile2 (~> 2.3.0)
     pg (1.0.0)
@@ -128,7 +129,8 @@ GEM
       byebug (~> 10.0)
       pry (~> 0.10)
     public_suffix (3.0.2)
-    puma (3.10.0)
+    puma (4.3.1)
+      nio4r (~> 2.0)
     rack (2.0.5)
     rack-protection (2.0.1)
       rack