That's a lie propagated by a pro-Kremlin blogger on Putin's payroll. No such thing happened.
Milley Flashback 2021
Gen. Milley Defends His Call To A Chinese General About Trump’s Rhetoric And The U.S.
Gen. Mark Milley says he was conducting the duties of his office — not circumventing presidential authority — when he spoke to his Chinese counterpart shortly before last year’s election, according to a statement the Pentagon issued Wednesday.
https://www.npr.org/2021/09/15/1037454733/milley-defends-call-to-chinese-general-about-trump