Revert "Fix a reference"

The sentence itself was not exact, [] and fetch are different. Reverting
in docrails because it has been reworded in master and 3-2-stable,see
98f4aee.

This reverts commit 6987966.

activesupport/lib/active_support/hash_with_indifferent_access.rb

@@ -96,7 +96,7 @@ def key?(key)
     alias_method :has_key?, :key?
     alias_method :member?, :key?
 
-    # Fetches the value for the specified key, same as doing <tt>hash[key]</tt>
+    # Fetches the value for the specified key, same as doing hash[key]
     def fetch(key, *extras)
       super(convert_key(key), *extras)
     end