Update Location documentation for altitude (WGS84 instead of sea level).

Change-Id: I9531fba75bc1fee7d0e7c1dc179e3d05fb3e8a42

location/java/android/location/Location.java

@@ -583,7 +583,8 @@ public class Location implements Parcelable {
     }
 
     /**
-     * Get the altitude if available, in meters above sea level.
+     * Get the altitude if available, in meters above the WGS 84 reference
+     * ellipsoid.
      *
      * <p>If this location does not have an altitude then 0.0 is returned.
      */
@@ -592,7 +593,7 @@ public class Location implements Parcelable {
     }
 
     /**
-     * Set the altitude, in meters above sea level.
+     * Set the altitude, in meters above the WGS 84 reference ellipsoid.
      *
      * <p>Following this call {@link #hasAltitude} will return true.
      */