Replace :base with :in [ci skip]

railties/lib/rails/generators/base.rb

@@ -83,7 +83,7 @@ def self.hide!
       #
       # The first and last part used to find the generator to be invoked are
       # guessed based on class invokes hook_for, as noticed in the example above.
-      # This can be customized with two options: :base and :as.
+      # This can be customized with two options: :in and :as.
       #
       # Let's suppose you are creating a generator that needs to invoke the
       # controller generator from test unit. Your first attempt is:
@@ -108,7 +108,7 @@ def self.hide!
       #   "test_unit:controller", "test_unit"
       #
       # Similarly, if you want it to also lookup in the rails namespace, you just
-      # need to provide the :base value:
+      # need to provide the :in value:
       #
       #   class AwesomeGenerator < Rails::Generators::Base
       #     hook_for :test_framework, in: :rails, as: :controller