Dissolution deed

You don’t need.

In Mohd. Laiquiddin and Anr. vs. Kamala Devi Misra (Dead) by L.Rs. and Ors.[3] it was held by Supreme Court at para 26 that-

“…when there are only two partners constituting the partnership firm, on the death of one of them, the firm is deemed to be dissolved despite the existence of a clause which says otherwise.