doc/git-bisect: clarify `git bisect run` syntax

The description of the `git bisect run` command syntax at the beginning of the manpage is `git bisect run <cmd>...`, which isn't quite clear about what `<cmd>` is or what the `...` mean; one could think that it is the whole (quoted) command line with all arguments in a single string, or that it supports multiple commands, or that it doesn't accept commands with arguments at all. Change to `git bisect run <cmd> [<arg>...]` to clarify the syntax, in both the manpage and the `git bisect -h` command output. Additionally, change `--term-{new,bad}` et al to `--term-(new|bad)` for consistency with the synopsis syntax conventions. Signed-off-by: Javier Mora <cousteaulecommandant@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>