rack.gemspec in rack-2.0.3 vs rack.gemspec in rack-2.0.4

@@ -10,11 +10,11 @@
 web applications in Ruby.  By wrapping HTTP requests and responses in
 the simplest way possible, it unifies and distills the API for web
 servers, web frameworks, and software in between (the so-called
 middleware) into a single method call.
 
-Also see http://rack.github.io/.
+Also see https://rack.github.io/.
 EOF
 
   s.files           = Dir['{bin/*,contrib/*,example/*,lib/**/*,test/**/*}'] +
                         %w(COPYING rack.gemspec Rakefile README.rdoc SPEC)
   s.bindir          = 'bin'
@@ -23,13 +23,12 @@
   s.extra_rdoc_files = ['README.rdoc', 'HISTORY.md']
   s.test_files      = Dir['test/spec_*.rb']
 
   s.author          = 'Christian Neukirchen'
   s.email           = '[e-mail]'
-  s.homepage        = 'http://rack.github.io/'
+  s.homepage        = 'https://rack.github.io/'
   s.required_ruby_version = '>= 2.2.2'
 
   s.add_development_dependency 'minitest', "~> 5.0"
   s.add_development_dependency 'minitest-sprint'
-  s.add_development_dependency 'concurrent-ruby'
   s.add_development_dependency 'rake'
 end