Bump puma from 3.12.2 to 3.12.3

Bumps [puma](https://github.com/puma/puma) from 3.12.2 to 3.12.3.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.12.2...v3.12.3)

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

Gemfile

@@ -44,7 +44,7 @@ gem 'pg', '0.21.0'
 # Heroku email service
 gem 'postmark-rails', '0.15.0'
 # Use Puma as the web server
-gem 'puma', '3.12.2'
+gem 'puma', '3.12.3'
 # Use Pundit for authorization
 gem 'pundit', '1.1.0'
 # Limits processing time in rack layer for added loading protection

Gemfile.lock

@@ -159,7 +159,7 @@ GEM
       method_source (~> 0.9.0)
     pry-rails (0.3.9)
       pry (>= 0.10.4)
-    puma (3.12.2)
+    puma (3.12.3)
     pundit (1.1.0)
       activesupport (>= 3.0.0)
     rack (2.0.8)
@@ -322,7 +322,7 @@ DEPENDENCIES
   pg (= 0.21.0)
   postmark-rails (= 0.15.0)
   pry-rails (~> 0.3.6)
-  puma (= 3.12.2)
+  puma (= 3.12.3)
   pundit (= 1.1.0)
   rack-timeout (= 0.4.2)
   rails (= 5.0.7.2)