If you are selling the property I wouldn't start a row over it, you would likely put off potential purchasers as any disputes will have to be disclosed.
A broken covenant can be enforced of course if anyone can be bothered. A lot of the time no one does bother. The house we moved into two years ago had various covenants on the leasehold, some were just plainly ridiculous others were in place for a restricted time whilst the builders finished the estate to keep it looking uniform. Those had expired about 10 years we bought it yet some hadn't. We have since bought the freehold and all those covenants have gone.
When we bought the house I spotted at least three of the current (at that time) covenants were being broken. It was suggested by the solicitor that these breaches were of no consequence to us and by their very nature no one would be bothered to take it to court as it would cost too much. You can also apply to get covenants removed especially if they can be considered unreasonable.
If it were me I would leave well alone as you are selling and avoid a load of hassle.