Erdős Problem 267: status mismatch (repo=formally solved, erdosproblems.com=open)

The status of [Erdős problem 267](https://www.erdosproblems.com/267) appears to have changed.

- **[This repo](http://github.com/google-deepmind/formal-conjectures/blob/main/FormalConjectures/ErdosProblems/267.lean)**: `formally solved` (in `FormalConjectures/ErdosProblems/267.lean`)
- **[erdosproblems.com/267](https://www.erdosproblems.com/267)**: `open`

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

Open FormalConjectures/ErdosProblems/267.lean and inspect its @[category research ...] annotation. Compare the repository status with the linked erdosproblems.com/267 page, then update the annotation if the status has changed; done means the repository metadata accurately reflects the verified status.

Written by the indexing model from the issue text.