re-word Preflight Fail msg, attempt 2
re-word Preflight Fail msg, attempt 2

My recent PR exceeded the 50 char limit (apparently the last character must be null?).

This new attempt changes: "Preflight Fail: Horizontal position estimate Error"  to: "Preflight Fail: Position estimate Error"

In fact, this newest wording is more easily understood by the average user and is actually more consistent with the other COM_ARM_EKF_xxx related errors:

COM_ARM_EKF_HGT --> "Preflight Fail: Height estimate Error"
COM_ARM_EKF_VEL --> "Preflight Fail: Velocity estimate Error"
COM_ARM_EKF_POS --> "Preflight Fail: Position estimate Error"
dagar/Firmware,PX4/Firmware,dagar/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,PX4/Firmware,PX4/Firmware,krbeverx/Firmware,krbeverx/Firmware,dagar/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,dagar/Firmware,dagar/Firmware,krbeverx/Firmware,PX4/Firmware,dagar/Firmware,acfloria/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,krbeverx/Firmware,PX4/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,acfloria/Firmware,PX4/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,PX4/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware