chore: upgrade to puma 5

Gemfile

@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 gem 'rails', '= 5.2.6.2'
 gem 'mysql2'
-gem 'puma', '~> 4'
+gem 'puma'
 gem 'turbolinks', '~> 5'
 gem 'haml'
 gem 'nifty-utils'

Gemfile.lock

@@ -151,7 +151,7 @@ GEM
     nokogiri (1.13.1)
       mini_portile2 (~> 2.7.0)
       racc (~> 1.4)
-    puma (4.3.11)
+    puma (5.6.2)
       nio4r (~> 2.0)
     racc (1.6.0)
     rack (2.2.3)
@@ -278,7 +278,7 @@ DEPENDENCIES
   nifty-utils
   nilify_blanks
   nio4r
-  puma (~> 4)
+  puma
   rails (= 5.2.6.2)
   resolv (~> 0.2.1)
   rspec

config/puma.rb

@@ -7,7 +7,3 @@ bind            "tcp://#{bind_address}:#{bind_port}"
 environment     Postal.config.rails&.environment || 'development'
 prune_bundler
 quiet false
-
-if ENV['APP_ROOT']
-  directory ENV['APP_ROOT']
-end