Small Quickstart explanation fixups

On about:torconnect, we mention Quickstart but it isn't obviously a reference to anything on that page (except, maybe, Always connect automatically, but that isn't clear). I think we should delete the sentence Quickstart allows Tor Browser to connect automatically. on that page.

On about:preferences#tor, we have a Quickstart section, and that uses the same text as about:torconnect, but it ends with Learn More where it links to general information about Tor - not information about Quickstart. Richard had the good idea of splitting the text and putting the first sentence under Tor Settings with Learn More, and keeping the second sentence about Quickstart under the Quickstart header.