Command docs: remove ellipses for '-rand'

Command docs: remove ellipses for '-rand'

Ellipses were used to express that the '-rand' value can specify
multiple files, like this:

    B<-rand> I<file...>

Because there are conventions around ellipses, this becomes confusing,
because '-rand file...' is normally intepreted to mean that
'-rand file1 file2 file3' would be processed as three randomness
files, which makes no sense.

Rather than making things complicated with more elaborate syntax, we
change it to:

    B<-rand> I<files>

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10065)