Remove unneeded code

railties/lib/rails/backtrace_cleaner.rb

@@ -26,17 +26,4 @@ module Rails
         add_filter { |line| line.sub(gems_regexp, '\2 (\3) \4') }
       end
   end
-
-  # For installing the BacktraceCleaner in the test/unit
-  module BacktraceFilterForTestUnit #:nodoc:
-    def self.included(klass)
-      klass.send :alias_method_chain, :filter_backtrace, :cleaning
-    end
-
-    def filter_backtrace_with_cleaning(backtrace, prefix=nil)
-      backtrace = filter_backtrace_without_cleaning(backtrace, prefix)
-      backtrace = backtrace.first.split("\n") if backtrace.size == 1
-      Rails.backtrace_cleaner.clean(backtrace)
-    end
-  end
 end