[Gemspec] Bump cocoapods-trunk to `~> 0.4.0`

cocoapods.gemspec

@@ -33,7 +33,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'cocoapods-downloader', '~> 0.7.2'
   s.add_runtime_dependency 'cocoapods-plugins',    '~> 0.3.1'
   s.add_runtime_dependency 'cocoapods-try',        '~> 0.4.2'
-  s.add_runtime_dependency 'cocoapods-trunk',      '~> 0.3.2'
+  s.add_runtime_dependency 'cocoapods-trunk',      '~> 0.4.0'
   s.add_runtime_dependency 'molinillo',            '~> 0.1.1'
 
   s.add_runtime_dependency 'colored',       '~> 1.2'