Update GeomagneticField coefficients to WMM-2020

Update the GeomagneticField coefficients according to the World
Magnetic Model 2020-2025 values and specify the base time in UTC since
calls to System.currentTimeMillis() will return a UTC based time.

Signed-off-by: Cory Hockenbury <chockenbury@gmail.com>
Change-Id: I7614d420ad55129b04e0dfa9310e39d715ed2da7