Remove flat_map compatibility layer.

Library/Homebrew/extend/enumerable.rb

@@ -1,13 +0,0 @@
-module Enumerable
-  unless method_defined?(:flat_map)
-    def flat_map
-      return to_enum(:flat_map) unless block_given?
-      r = []
-      each do |*args|
-        result = yield(*args)
-        result.respond_to?(:to_ary) ? r.concat(result) : r.push(result)
-      end
-      r
-    end
-  end
-end

Library/Homebrew/global.rb

@@ -4,7 +4,6 @@ require "extend/pathname"
 require "extend/git_repository"
 require "extend/ARGV"
 require "extend/string"
-require "extend/enumerable"
 require "os"
 require "utils"
 require "exceptions"