In my opinion, it does not really matter and I would leave it alone. This assumes that the ground strap is properly connected at both ends.
I used to work in military electronics manufacturing and we used a term called 'gas tight connections'. This applied to crimps, old fashioned wire wraps and mechanical lug connections. Basically, the two metal surfaces are is such tight and close contact that no gas (or liquid) could come between them. Hence there is no possibility of corrosion that would degrade the electrical connection.
I'm sure that you have witnessed this when taking something really old/corroded apart and been surprised to see that under a mechanical connection that it looks brand new.
For your ground strap, if the connections are tight, I would leave them alone. Also, cleaning the copper surface corrosion will do absolutely nothing to improve your electrical performance. You do want the strap clean and the whole area free of acids and salts (vinegar is a mild acid).
I am an electrical engineer but do not pretend to be an expert at everything. Hope you get other worthwhile advice.
Cheers!