Azure: Correct comment about the strategy in the world matrix build

At this point noting that we have a split in our job similar to TravisCI
(which we have not used in years) isn't helpful, and is also not true
anymore either. Instead, explain that we split the world up in to 10
jobs as that's the maximum we can have going in parallel on the free
tier of Azure.

Signed-off-by: Tom Rini <trini@konsulko.com>