[j-nsp] upgrading an antique 240

[Randy Bush]

> Good point! TSB16735 says last version of Junos to support SCB-MX960 is 16.2
> 
>> Junos 17.3R3-S10
>> Junos 18.4R2-S5
>> Junos 19.3R3-S2
>> Junos 19.4R3-S3

so which steps to get from 14 to 16.2?  15.x 16.2?

randy