help: note the option name on option incompatibility

help: note the option name on option incompatibility

Change the errors added in d35d03cf93e (help: simplify by moving to
OPT_CMDMODE(), 2021-09-22) to quote the offending option at the user
when invoked as e.g.:

    git help --guides garbage

Now instead of:

    fatal: this option doesn't take any other arguments

We'll emit:

    fatal: the '--guides' option doesn't take any non-option arguments

Let's also rename the function, as it will be extended to do other
checks that aren't "no extra argc" in a subsequent commit.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>