Remove classifier text and replace with external link

[Oddant1]

Replace the classifier stuff in the docs with a link to https://resources.qiime2.org

[Oddant1]

Do we want that first note there or not? The way the code is flowed suggests it's supposed to be associated with the Marker gene reference databases section, but it looks awkward, and there is already another copy of that note at the bottom of that section.

[Oddant1]

Looks like this without the note, I think without is much better I only ask because like I said the way the code is written looks like the intent is for the note to be associated with the section beneath it

[gregcaporaso]

@Oddant1, we don't need that note, so let's go with your second example above. I suspect that note was just misplaced with respect to the anchor that follows it right now.

This is ready for merge once you remove that note. Thank you!