Bump puma from 3.12.1 to 3.12.6

Bumps [puma](https://github.com/puma/puma) from 3.12.1 to 3.12.6.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.12.1...v3.12.6)

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

Gemfile

@@ -13,7 +13,7 @@ end
 group :production do
   gem 'pg'
 end# Use Puma as the app server
-gem 'puma', '~> 3.11'
+gem 'puma', '~> 3.12'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5'
 # Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker

Gemfile.lock

@@ -105,7 +105,7 @@ GEM
       mini_portile2 (~> 2.4.0)
     pg (1.1.4)
     public_suffix (3.1.1)
-    puma (3.12.1)
+    puma (3.12.6)
     rack (2.0.7)
     rack-proxy (0.6.5)
       rack
@@ -208,7 +208,7 @@ DEPENDENCIES
   jbuilder (~> 2.7)
   listen (>= 3.0.5, < 3.2)
   pg
-  puma (~> 3.11)
+  puma (~> 3.12)
   rails (~> 6.0.0)
   sass-rails (~> 5)
   selenium-webdriver