[j-nsp] Woot. Updated MX software recommendation

[OBrien, Will]

I got on TAC about the fact that they were recommending 10.4 code for the MX when it doesn't support the Enhanced SCB at all.
I don't know if it was my case or just enough people giving them a hard time, but they notified me that they've updated KB21476.

There is now an entry for the MX series and the MX series with the Enhanced SCB. (11.2R5.4 at this time.)

Will