Green's Open Problems #80

### What is the conjecture
https://people.maths.ox.ac.uk/greenbj/papers/open-problems.pdf#problem.80

Find bounds in the classification theorem for approximate groups.

### [AMS categories](https://github.com/google-deepmind/formal-conjectures/labels?q=ams-)

* ams-20

### Choose either option
- [ ] I plan on adding this conjecture to the repository
- [x] This issue is up for grabs: I would like to see this conjecture added by somebody else

Start with the linked Green open-problems PDF and read problem 80, then review the repository's existing formalized conjecture statements and contribution conventions. Determine the precise bounds that must be formalized; done means the conjecture is added in Lean and passes the repository's checks.

Written by the indexing model from the issue text.