Fixed malformed attribute directives in docs.

[smithdc1]

I think the two attribute changes are fairly straight forward.

While looking for other cases I found the comment one, not sure what this was intended for but it's been there for about a decade and doesn't show in the docs. Therefore I thought we could remove it?

I've put as two separate commits so the second one can be dropped/squashed as needed.

[bmispelon]

Changes look good, thanks 👍🏻

I checked for other missing colons using git grep -E '\.\. attribute:[^:]' -- docs/ and only found the two you've fixed.
I also agree with your removal of the .. comment (there are no other usage of .. comment in the docs).

[felixxm]

@smithdc1 Thanks 👍