Add reminder to validator to check the MB-wide lab ID list!

[mekline]

Lab IDs are really important for our datasets! Especially tracking & merging across the datasets. We've added reminders to the manual to check that, but also add a reference to the mega list here!

https://docs.google.com/spreadsheets/d/1O_c4QoRwBUQvpCABFC2XIlx4upsvHZm02VDV8xDUg8s/edit?usp=sharing