Update referrer-trimming after Windows rollout & clarify cookie pop-up mechanics

[laghee]

We've now released referrer header trimming on Windows, and wanted to clarify Cookie Pop-up Management function with a reference to Easylist now that we've started using their rules as well.

@alohaas, I dropped the hyphen in "open-source lists" here (and zapped the only other instance I found in the page) as the easiest path to consistency. We aren't currently using a hyphen in "open source code," which is everywhere in the doc (and involves a lot of links, so I'm a little concerned that would look busy), or a couple other instances of "open source list." However, no strong feelings about it, so I can go the other way if we want to instead add the hyphen everywhere that it technically qualifies as an adjective usage before a noun 😁 🤷‍♀️