Merge branch 'upgrade-thin' into 'master'

Upgrade Thin from 1.6.1 to 1.7.0.

Includes support for Rack 2. Working toward #14286.

Changelog: https://github.com/macournoyer/thin/blob/master/CHANGELOG

See merge request !5047

Gemfile

@@ -264,7 +264,7 @@ group :development do
   gem "sdoc", '~> 0.3.20'
   # thin instead webrick
-  gem 'thin', '~> 1.6.1'
+  gem 'thin', '~> 1.7.0'
 end
 group :development, :test do

Gemfile.lock

@@ -725,10 +725,10 @@ GEM
     temple (0.7.7)
     test_after_commit (0.4.2)
       activerecord (>= 3.2)
-    thin (1.6.4)
+    thin (1.7.0)
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)
-      rack (~> 1.0)
+      rack (>= 1, < 3)
     thor (0.19.1)
     thread_safe (0.3.5)
     tilt (2.0.5)
@@ -970,7 +970,7 @@ DEPENDENCIES
   teaspoon (~> 1.1.0)
   teaspoon-jasmine (~> 2.2.0)
   test_after_commit (~> 0.4.2)
-  thin (~> 1.6.1)
+  thin (~> 1.7.0)
   tinder (~> 1.10.0)
   turbolinks (~> 2.5.0)
   u2f (~> 0.2.1)