cmd/cue/cmd: fix --dryrun flag description of import command
The '--dryrun' flag description is the same as '--force' flag and it's wrong.
Copy from `add` command's '--dryrun' flag description.
Change-Id: Ie3d77a2f2e2e45da9e513ded6636402fce276876
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/3060
Reviewed-by: Marcel van Lohuizen <mpvl@google.com>
authored by