What should I do about Reliance AMC funds in my portfolio?

Please note this important feature of the structure of a mutual fund.  The AMC (in this case Reliance AMC) only makes decisions regarding the investments of the funds pooled in from the investors. The actual units and the money are with the custodian.  If an AMC is facing trouble, the future decisions may be an in issue - but there is little danger in the current units.

In any case, Reliance has already agreed to sell its stake to the partner Nippon Life and the transaction would close soon. The name of the company has already been changed to include Nippon Life.  https://www.reliancemutual.com/about-us/company-profile/reliance-nippon-life-asset-management-limited/

In the past too, I am not aware of any AMC actually going completely down. They have always transitioned their business (cleanly) to another entity.