Revert "Add missing require"

This reverts commit e4b33b08.

https://github.com/rails/rails/pull/7452#issuecomment-8094302

actionpack/test/dispatch/session/mem_cache_store_test.rb

 require 'abstract_unit'
-require 'fixtures/session_autoload_test/session_autoload_test/foo'
 
 # You need to start a memcached server inorder to run these tests
 class MemCacheStoreTest < ActionDispatch::IntegrationTest