builtin/remote.c: parse options in 'rename'

builtin/remote.c: parse options in 'rename'

The 'git remote rename' command doesn't currently take any command-line
arguments besides the existing and new name of a remote, and so has no
need to call parse_options().

But the subsequent patch will add a `--[no-]progress` option, in which
case we will need to call parse_options().

Do so now so as to avoid cluttering the following patch with noise, like
adjusting setting `rename.{old,new}_name` to argv[0] and argv[1], since
parse_options handles advancing argv past the name of the sub-command.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>