Autoload show notice option

[jdevalk]

When I check which options are being requested during a page load, I see a "cache miss" for duplicate_post_show_notice quite often, because that option isn't autoloaded. I would suggest adding autoload to it or not requesting it as much.

I've been keeping track using my own AAA Option Optimizer plugin of which options get requested a lot but aren't autoloaded and on my test site, this option was the worst offender.

• [x] I've searched for any related issues and avoided creating a duplicate issue.