Bug#939581: firefox: problem seems to be solved with 69.0.2-1

[Sanjoy Mahajan]

I'm now using firefox 69.0.2-1 (amd64), and the problem seems to have
solved itself (or maybe Mozilla noticed and fixed it?).  That is, the
print dialog now selects (by highlighting in blue) my CUPS default
printer as its default printer.

-Sanjoy