[ios] Remove double counting of content inset top and bottom (#6566)

This removes the calls to top and bottom for content inset of the
map view when calculating the edge padding for following. A previous
commit added this along with the left and right values. This
eliminates a bug where the map did not scroll to the correct location
for the user dot and also a bug in
`didUpdateLocationWithUserTrackingAnimated:` where the map panning
operations would always occur because the current and correct points
never matched up even if a stream of location values that were the
same were processed.

platform/ios/src/MGLMapView.mm

@@ -4173,9 +4173,9 @@ public:
     CGRect boundsAroundCorrectPoint = CGRectOffset(bounds,
                                                    correctPoint.x - CGRectGetMidX(bounds),
                                                    correctPoint.y - CGRectGetMidY(bounds));
-    return UIEdgeInsetsMake(CGRectGetMinY(boundsAroundCorrectPoint) - CGRectGetMinY(bounds) + self.contentInset.top,
+    return UIEdgeInsetsMake(CGRectGetMinY(boundsAroundCorrectPoint) - CGRectGetMinY(bounds),
                             self.contentInset.left,
-                            CGRectGetMaxY(bounds) - CGRectGetMaxY(boundsAroundCorrectPoint) + self.contentInset.bottom,
+                            CGRectGetMaxY(bounds) - CGRectGetMaxY(boundsAroundCorrectPoint),
                             self.contentInset.right);
 }