Confirm vectorised constraint usage

[wtgee]

(wtgee: Adding this comment from a stale (closed) issue):

I believe so, although we should probably open a separate, but related, issue, since at the moment I think you can actually create a Constraint with a vectorised list of constraints quite happily, but I'm not sure it broadcasts sensibly when used...

Originally posted by @StuartLittlefair in https://github.com/astropy/astroplan/issues/189#issuecomment-550435883