uxrce_client: Do not send PositionSetpointTriplet

There is no one using the position_setpoint_triplet messages
in MC side currently and because no users there, it causes
SROS ACL errors about uxrce-agent has no permissions to write
to topic.

src/modules/uxrce_dds_client/dds_topics.yaml

@@ -11,9 +11,6 @@ publications:
   - topic: /fmu/out/failsafe_flags
     type: px4_msgs::msg::FailsafeFlags
 
-  - topic: /fmu/out/position_setpoint_triplet
-    type: px4_msgs::msg::PositionSetpointTriplet
-
   - topic: /fmu/out/sensor_combined
     type: px4_msgs::msg::SensorCombined