reset: show --no-refresh in the short-help

reset: show --no-refresh in the short-help

In the short help output from "git reset -h", the recently added
"--[no-]refresh" option is shown like so:

        --refresh             skip refreshing the index after reset

which explains what happens when the option is given in the negative
form, i.e. "--no-refresh".  We could rephrase the explanation to
read "refresh the index after reset (default)" to hint that the user
can say "--no-refresh" to override the default, but listing the
"--no-refresh" form in the list of options would be more helpful.

Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Acked-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>