Update path_longer_on_approach.cpp (#4344)

Fix the bug that isPathUpdated function will return false for the reason that it compare the timestaped between new path and old path's last pose

Signed-off-by: StetroF <120172218+StetroF@users.noreply.github.com>

nav2_behavior_tree/plugins/decorator/path_longer_on_approach.cpp

@@ -36,7 +36,7 @@ bool PathLongerOnApproach::isPathUpdated(
 {
  return new_path != old_path && old_path.poses.size() != 0 &&
  new_path.poses.size() != 0 &&
- old_path.poses.back() == new_path.poses.back();
+ old_path.poses.back().pose == new_path.poses.back().pose;
 }
 
 bool PathLongerOnApproach::isRobotInGoalProximity(