[ranges.syn] Fix `// freestanding` comments of under [range.as.rvalue]

[JohelEGP]

#5708 (comment) was not applied and its surrounding // freestanding comments are not aligned with the rest. See the discussion starting at #5698 (comment) as for why the linked suggestion makes sense, besides having been what the paper requested.

[tkoeppe]

I've got this already, thanks.

[tkoeppe]

Splitting the alignment and the missing comment and sending a PR for the latter.