scriptreplay: reduce two usage synopses to one, and drop the -t from it

scriptreplay: reduce two usage synopses to one, and drop the -t from it

Those two synopses still did not express several possible forms:

    scriptreplay -m.1 timings
    scriptreplay typescript -t timings -m.1
    ...

So, instead of trying to cover all possibilities, just give the
basic form of the command, which is clearest and most helpful.

Signed-off-by: Benno Schulenberg <bensberg@telfort.nl>