Revert "PERF: send Content-Length from Rails on all requests"

This reverts commit ea0e238ae1.

Does not seem needed reverting

config/initializers/300-content_length.rb

@@ -1,37 +0,0 @@
-# Just like Rack except we dont do a to_ary check so we can calculate length
-# on body proxy objects
-# Sets the Content-Length header on responses with fixed-length bodies.
-class ContentLength
-  TRANSFER_ENCODING = "Transfer-Encoding".freeze
-  CONTENT_LENGTH = "Content-Length".freeze
-
-  include Rack::Utils
-
-  def initialize(app)
-    @app = app
-  end
-
-  def call(env)
-    status, headers, body = @app.call(env)
-
-    if !STATUS_WITH_NO_ENTITY_BODY.include?(status.to_i) &&
-       !headers[CONTENT_LENGTH] &&
-       !headers[TRANSFER_ENCODING]
-
-      obody = body
-      body, length = [], 0
-      obody.each { |part| body << part; length += part.bytesize }
-
-      body = Rack::BodyProxy.new(body) do
-        obody.close if obody.respond_to?(:close)
-      end
-
-      headers[CONTENT_LENGTH] = length.to_s
-    end
-
-    [status, headers, body]
-  end
-end
-
-# content length helps us instruct NGINX on how to deal with this
-Rails.configuration.middleware.unshift ContentLength