docs, It's "Active Job" not "Active job". [ci skip]

activejob/lib/active_job/base.rb

@@ -9,14 +9,14 @@
 module ActiveJob #:nodoc:
   # = Active Job
   #
-  # Active job objects can be configured to work with different backend
+  # Active Job objects can be configured to work with different backend
   # queuing frameworks. To specify a queue adapter to use:
   #
   #   ActiveJob::Base.queue_adapter = :inline
   #
   # A list of supported adapters can be found in QueueAdapters.
   #
-  # Active job objects can be defined by creating a class that inherits
+  # Active Job objects can be defined by creating a class that inherits
   # from the ActiveJob::Base class. The only necessary method to
   # implement is the "perform" method.
   #