docs(*): Wrap some links in < … > (#13852)
I noticed that many docs say
See https://stacks.math.columbia.edu/tag/001T.
and the our documentation will include the final `.` in the URL, causing
the URL to not work.
This tries to fix some of these instances. I intentionally applied this
to some URLs ending with a space, because it does not hurt to be
explicit, and the next contributor cargo-culting the URL is more likely
to get this right.
Obligatory xkcd reference: https://xkcd.com/208/
