Bump puma from 4.3.12 to 5.6.8

Bumps [puma](https://github.com/puma/puma) from 4.3.12 to 5.6.8.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v4.3.12...v5.6.8)

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

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

Gemfile

@@ -12,7 +12,7 @@ gem 'rails', '~> 5.1.7'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 4.3'
+gem 'puma', '~> 5.6'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets

Gemfile.lock

@@ -134,13 +134,13 @@ GEM
     mini_mime (1.0.2)
     mini_portile2 (2.8.0)
     minitest (5.17.0)
-    nio4r (2.5.2)
+    nio4r (2.7.1)
     nokogiri (1.13.10)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     pg (1.2.0)
     public_suffix (4.0.6)
-    puma (4.3.12)
+    puma (5.6.8)
       nio4r (~> 2.0)
     racc (1.6.1)
     rack (2.2.9)
@@ -237,7 +237,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
   pg (>= 0.18, < 2.0)
-  puma (~> 4.3)
+  puma (~> 5.6)
   rails (~> 5.1.7)
   rspec-core!
   rspec-expectations!