The end result of the flawed UA spoofer was to accomplish the
OPPOSITE of the intended goal. UA spoofing for privacy purpose
turns out to be a whole complicated task on its own, and is
best undertaken as a separate dedicated extension -- assuming
it is possible at all.
In any case, this had no place in a "Privacy" section in uMatrix,
this was a bad idea to create this feature in the first place. It's
never too late to correct a bad idea, and this is the purpose of
this commit.