[wtp-releng] Correction to our M6 date: 3/20 --> 3/18

[David M Williams <david_williams@xxxxxxxxxx>]

Apologies for not noticing this until now,
but our WTP schedules until now have said our M6 was due 3/20.
But I just noticed that the Galileo +2 date was 3/18!

Since that final week was "test and shutdown" week, hopefully everyone can adjust and finish their testing a few days earlier.

Let me know if pulling in our date to the 18th causes any problems that I can help solve.

Thanks,