Erdős Problem 48: status mismatch (repo=solved, erdosproblems.com=formally solved)

The status of [Erdős problem 48](https://www.erdosproblems.com/48) appears to have changed.

- **[This repo](http://github.com/google-deepmind/formal-conjectures/blob/main/FormalConjectures/ErdosProblems/48.lean)**: `solved` (in `FormalConjectures/ErdosProblems/48.lean`)
- **[erdosproblems.com/48](https://www.erdosproblems.com/48)**: `formally solved`

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

Open FormalConjectures/ErdosProblems/48.lean and inspect its @[category research ...] annotation alongside the current status on erdosproblems.com/48. Verify whether the repository status is outdated, then update the annotation if appropriate; done means the local status matches the verified external status.

Written by the indexing model from the issue text.