Update MechJebModuleDockingAutopilot.cs

Changed approachSpeedMult from 1 to 6 checked with 10 different ships from 13 to 120tons docking worked better with this setting. at 9 I did have problems with 100 ship coasting past docking axis before being able to stop. at 6 the problem did not exsist and smalled ship docking became alot faster.