A US Army sentinel guarding the Tomb of the ​Unknown ​Soldier appeared to ​rebuke Defence Secretary Pete Hegseth's delegation ⁠on Wednesday after laughter could be heard ⁠as they climbed the steps of ​the solemn site, according to a video of the incident.Mr Hegseth, his wife and ⁠senior aides could be seen taking pictures and speaking to each other on the steps of the memorial at Arlington National Cemetery following a Veterans Day…