Standalone instructions contradictionary

The [current `certonly` instructions](https://github.com/certbot/website/blob/942e5bf17cdb0e989dc4ba0e5657dff92ac5faf9/_scripts/instruction-widget/templates/getting-started/certonly.html#L12-L22) is kinda contradictionary and incomplete IMHO.

I'll quote the pieces which are bothering me:

> Are you ok with temporarily stopping your website?

This makes the **assumption** people have a website running. This is not always the case, for example, when someone only runs a mailserver on the host.

The line after that states:

> Yes, my web server is not currently running on this machine.

This is contradictionary with the previous question: "stopping a website" means it's running. And the "Yes" answers the previous question, which "confirms" a website is actually running. But the other part of the sentence says it's **not** running? That doesn't compute..

The next sentence:

> Stop your webserver (…)

Also seems to make you think the webserver is actually running.

So for me, there are two issues with these three sentences:

a) It assumes the server has a website running, which is not always the case;
b) The second sentence, about "webserver is not running", is not in line with the sentence above and below it.

I would recommend rewriting this part also when the `certonly` instruction is being rewritten for https://github.com/certbot/website/issues/496 which also addresses a valid issue about the certonly instructions.