remote: simplify "remote add --tags" help text
The help text for the --tags option was split into two option[]
entries, which was a hacky way to give two lines of help text (the
second entry did not have either short or long help, and there was
no way to invoke its entry---it was there only for the help text).
As we now support multi-line text in the option help, let's make
the second line of the help a proper second line and remove the
hacky second entry.
Signed-off-by: Junio C Hamano <gitster@pobox.com>