Erdős Problem 730: status mismatch (repo=open, erdosproblems.com=solved)

The status of [Erdős problem 730](https://www.erdosproblems.com/730) appears to have changed.

- **[This repo](http://github.com/google-deepmind/formal-conjectures/blob/main/FormalConjectures/ErdosProblems/730.lean)**: `open` (in `FormalConjectures/ErdosProblems/730.lean`)
- **[erdosproblems.com/730](https://www.erdosproblems.com/730)**: `solved`

Please verify and update the `@[category research ...]` annotation if appropriate.

Start with FormalConjectures/ErdosProblems/730.lean and compare its status with the linked Erdős Problems page at erdosproblems.com/730. Verify whether the problem is solved, then update the @[category research ...] annotation if appropriate; done means the repository status matches the verified external status.

Written by the indexing model from the issue text.