adds deprecation warnings to the RDoc of Array#uniq_by(!)

activesupport/lib/active_support/core_ext/array/uniq_by.rb

 class Array
-  # Returns an unique array based on the criteria given as a +Proc+.
+  # *DEPRECATED*: Use +Array#uniq+ instead.
+  #
+  # Returns a unique array based on the criteria in the block.
   #
   #   [1, 2, 3, 4].uniq_by { |i| i.odd? } # => [1, 2]
   #
@@ -9,7 +11,9 @@ def uniq_by(&block)
     uniq(&block)
   end
 
-  # Same as uniq_by, but modifies self.
+  # *DEPRECATED*: Use +Array#uniq!+ instead.
+  #
+  # Same as +uniq_by+, but modifies +self+.
   def uniq_by!(&block)
     ActiveSupport::Deprecation.warn "uniq_by! " \
       "is deprecated. Use Array#uniq! instead", caller