Freeze v6.0 Branch, Clone it mobile_app_closed

[Mostelk]

@farook-edev @anhappdev let us freeze v6.0 branch at the latest 5e5472d

@freedomtan please update branch submission-v6.0_open with above commit

in https://github.com/mlcommons/mobile_app_closed for our submission, all submitters @AhmedTElthakeb @mohitmundhragithub @PeggieLu need make a PR against this new branch https://github.com/mlcommons/mobile_app_closed/tree/submission-v6.0_open

[freedomtan]

Let's leave this open until we finished submission.