A few days prior to the end of the transition period on June 30, 2021, the EU Commission published its decision (adequacy decision) establishing an appropriate level of data protection for the UK in relation to the EU. This means that data transfers to the UK are treated as though the UK were still a member of the EU.
In this respect - apart from the potential requirement of a data protection agreement - no special contractual provisions nor a complete discontinuation of data transfers to the UK are required.