GnssLocationProvider metrics race condition fix

setting mLastFixTime = 0 in stopNavigating() introduces race condition where
if a fix is reported back from HAL milliseconds after stopNavigating() is
called, there will be a long TTFF calculated.

Bug: 70747938
Change-Id: I4868fd5ff6a1c072581e7825ac48ff1878833436

services/core/java/com/android/server/location/GnssLocationProvider.java

@@ -1582,7 +1582,6 @@ public class GnssLocationProvider implements LocationProviderInterface {
             mStarted = false;
             mSingleShot = false;
             native_stop();
-            mTimeToFirstFix = 0;
             mLastFixTime = 0;
 
             // reset SV count to zero