DEV: Remove a perf fix that's no longer needed

It has been added to Rails in cc2d614e63 (v6.0.0.beta2)

lib/freedom_patches/performance_fixes.rb

@@ -1,23 +0,0 @@
-# frozen_string_literal: true
-
-# perf fixes, review for each rails upgrade.
-
-# This speeds up calls to present? and blank? on model instances
-# Eg: Topic.new.blank? (which is always false) and so on.
-#
-# Per: https://gist.github.com/SamSaffron/c8bbc8c7b6bf3b0148760c887df18b55
-# Comparison:
-#         fast present: 25253295.0 i/s
-#       fast present 2: 24623199.7 i/s - same-ish: difference falls within error
-#         slow present:   335003.0 i/s - 75.38x  slower
-#       slow present 2:   275212.8 i/s - 91.76x  slower
-#
-#  raised with rails at: https://github.com/rails/rails/issues/35059
-class ActiveRecord::Base
-  def present?
-    true
-  end
-  def blank?
-    false
-  end
-end