Removed humidity effect on bullet trajectory. See #995

Reasons:
- The effect is almost negligible. Its many times lower than both altitude and temperature (which are currently not considered); it's probably also lower than Coriolis and powder temperature (see #995).
- We currently have the effect reversed; although unintuitive, moist air is in fact lighter than dry air. Velocity should in any case be reduced when humidity is 0, not 100% (see #995).
- Our current implementation relies on Arma 3 humidity command, which behaves nothing like real humidity (not even close, see https://community.bistudio.com/wiki/humidity).

If anything, altitude and temperature (and optionally powder temp) should be the things to consider.