monogdb3 - removal query/proposal

[Greg Troxel <gdt%lexort.com@localhost>]

This note is partly to withdraw any objections I may have made about
removing mongodb3.  I have just dropped MAINTAINERship.

mongodb3 is the last Free Software version, but it's unmaintained and
I'm not sure anybody cares or uses it.  We have mongodb4 and mongodb (6).

unifi 6 used mongodb3, but now we have unifi 8 that uses mongodb4 (and
perhaps mongodb6, if it can be built).  I used to insist that mongodb3
stay because of unifi.

I can't find any DEPENDS of mongodb3, but the only DEPENDS on any
mongodb is from unifi.  This doesn't seem right.

I'm not really anxious to rm it, but my perception is that it stayed
only because of unifi, so it seems only fair to wakeup() the gc thread.
Thus if nobody cares we might as well drop it.

Does anybody use mongodb beyond unifi, and in particular mongodb3?
Does anybody want it to stay, or think it should?