Update Puma to v4.3.0

This is the changeset:
https://github.com/puma/puma/compare/v3.12.0..v4.3.0

Gemfile

@@ -170,8 +170,8 @@ group :unicorn do
 end
 
 group :puma do
-  gem 'puma', '~> 3.12', require: false
-  gem 'puma_worker_killer', require: false
+  gem 'puma', '~> 4.3.0', require: false
+  gem 'puma_worker_killer', '~> 0.1.1', require: false
   gem 'rack-timeout', require: false
 end
 

Gemfile.lock

@@ -749,10 +749,11 @@ GEM
     pry-rails (0.3.6)
       pry (>= 0.10.4)
     public_suffix (3.1.1)
-    puma (3.12.0)
-    puma_worker_killer (0.1.0)
+    puma (4.3.0)
+      nio4r (~> 2.0)
+    puma_worker_killer (0.1.1)
       get_process_mem (~> 0.2)
-      puma (>= 2.7, < 4)
+      puma (>= 2.7, < 5)
     pyu-ruby-sasl (0.0.3.3)
     raabro (1.1.6)
     rack (2.0.7)
@@ -1280,8 +1281,8 @@ DEPENDENCIES
   prometheus-client-mmap (~> 0.9.10)
   pry-byebug (~> 3.5.1)
   pry-rails (~> 0.3.4)
-  puma (~> 3.12)
-  puma_worker_killer
+  puma (~> 4.3.0)
+  puma_worker_killer (~> 0.1.1)
   rack (~> 2.0.7)
   rack-attack (~> 6.2.0)
   rack-cors (~> 1.0.0)