Bump puma from 3.12.4 to 4.3.9

Bumps [puma](https://github.com/puma/puma) from 3.12.4 to 4.3.9.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.12.4...v4.3.9)

---
updated-dependencies:
- dependency-name: puma
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Diff for: Gemfile

@@ -1,4 +1,4 @@
 source 'https://rubygems.org'
 
 gem "rack", "~> 2.1"
-gem "puma", "~> 3.12"
+gem "puma", "~> 4.3"

Diff for: Gemfile.lock

@@ -1,14 +1,16 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    puma (3.12.4)
+    nio4r (2.5.8)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.1.4)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
-  puma (~> 3.12)
+  puma (~> 4.3)
   rack (~> 2.1)
 
 BUNDLED WITH