Refer to the library name instead of the constant

When we are loading a component and we want to know its version, we are
actually not speaking about the constant but the library itself.

[ci skip]

[Godfrey Chan & Xavier Noria]

actionmailer/lib/action_mailer/gem_version.rb

 module ActionMailer
-  # Returns the version of the currently loaded ActionMailer as a <tt>Gem::Version</tt>
+  # Returns the version of the currently loaded Action Mailer as a <tt>Gem::Version</tt>
   def self.gem_version
     Gem::Version.new VERSION::STRING
   end

actionpack/lib/action_pack/gem_version.rb

 module ActionPack
-  # Returns the version of the currently loaded ActionPack as a <tt>Gem::Version</tt>
+  # Returns the version of the currently loaded Action Pack as a <tt>Gem::Version</tt>
   def self.gem_version
     Gem::Version.new VERSION::STRING
   end

actionview/lib/action_view/gem_version.rb

 module ActionView
-  # Returns the version of the currently loaded ActionView as a <tt>Gem::Version</tt>
+  # Returns the version of the currently loaded Action View as a <tt>Gem::Version</tt>
   def self.gem_version
     Gem::Version.new VERSION::STRING
   end

activejob/lib/active_job/gem_version.rb

 module ActiveJob
-  # Returns the version of the currently loaded ActiveJob as a <tt>Gem::Version</tt>
+  # Returns the version of the currently loaded Active Job as a <tt>Gem::Version</tt>
   def self.gem_version
     Gem::Version.new VERSION::STRING
   end

activemodel/lib/active_model/gem_version.rb

 module ActiveModel
-  # Returns the version of the currently loaded ActiveModel as a <tt>Gem::Version</tt>
+  # Returns the version of the currently loaded Active Model as a <tt>Gem::Version</tt>
   def self.gem_version
     Gem::Version.new VERSION::STRING
   end

activerecord/lib/active_record/gem_version.rb

 module ActiveRecord
-  # Returns the version of the currently loaded ActiveRecord as a <tt>Gem::Version</tt>
+  # Returns the version of the currently loaded Active Record as a <tt>Gem::Version</tt>
   def self.gem_version
     Gem::Version.new VERSION::STRING
   end

activesupport/lib/active_support/gem_version.rb

 module ActiveSupport
-  # Returns the version of the currently loaded ActiveSupport as a <tt>Gem::Version</tt>
+  # Returns the version of the currently loaded Active Support as a <tt>Gem::Version</tt>
   def self.gem_version
     Gem::Version.new VERSION::STRING
   end