fix warning

Author: facontidavide

src/decorators/wait_update.cpp

@@ -10,8 +10,6 @@
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-#pragma once
-
 #include "behaviortree_cpp/decorators/wait_update.h"
 
 namespace BT