upstream: Call comma-separated lists as such to clarify semantics

upstream: Call comma-separated lists as such to clarify semantics

Options such as Ciphers take values that may be a list of ciphers;  the
complete list, not indiviual elements, may be prefixed with a dash or plus
character to remove from or append to the default list respectively.

Users might read the current text as if each elment took an optional prefix,
so tweak the wording from "values" to "list" to prevent such ambiguity for
all options supporting this semantics (those that provide a list of
available elements via "ssh -Q ...").

Input and OK jmc

OpenBSD-Commit-ID: 4fdd175b0e5f5cb10ab3f26ccc38a93bb6515d57