Erdős Problem 442: status mismatch (repo=solved, erdosproblems.com=formally solved)

The status of [Erdős problem 442](https://www.erdosproblems.com/442) appears to have changed.

- **[This repo](http://github.com/google-deepmind/formal-conjectures/blob/main/FormalConjectures/ErdosProblems/442.lean)**: `solved` (in `FormalConjectures/ErdosProblems/442.lean`)
- **[erdosproblems.com/442](https://www.erdosproblems.com/442)**: `formally solved`

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

Open FormalConjectures/ErdosProblems/442.lean and compare its @[category research ...] annotation with the status shown at erdosproblems.com/442. Verify whether the problem is formally solved, then update the annotation if needed. Done means the repository status matches the external problem page.

Written by the indexing model from the issue text.