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

@@ -8,7 +8,7 @@ gem 'rails', '~> 6.0.0'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3', '~> 1.4'
 # 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

@@ -213,7 +213,7 @@ GEM
     orm_adapter (0.5.0)
     popper_js (1.14.5)
     public_suffix (4.0.1)
-    puma (3.12.1)
+    puma (3.12.6)
     rack (2.0.7)
     rack-protection (2.0.7)
       rack
@@ -354,7 +354,7 @@ DEPENDENCIES
   omniauth-facebook (~> 5.0)
   omniauth-github (~> 1.3)
   omniauth-twitter (~> 1.4)
-  puma (~> 3.11)
+  puma (~> 3.12)
   rails (~> 6.0.0)
   sass-rails (~> 5)
   selenium-webdriver