Fixed AnimationTreeStateMachine transition priority (last transition was always chosen instead of least cost)

Fixes #31132

(cherry picked from commit aaad50e4d9)

scene/animation/animation_node_state_machine.cpp

@@ -235,6 +235,7 @@ bool AnimationNodeStateMachinePlayback::_travel(AnimationNodeStateMachine *sm, c
 
 			if (cost < least_cost) {
 				least_cost_transition = E;
+				least_cost = cost;
 			}
 		}