Erdős Problem 175: status mismatch (repo=solved, erdosproblems.com=formally solved)

The status of [Erdős problem 175](https://www.erdosproblems.com/175) appears to have changed.

- **[This repo](http://github.com/google-deepmind/formal-conjectures/blob/main/FormalConjectures/ErdosProblems/175.lean)**: `solved` (in `FormalConjectures/ErdosProblems/175.lean`)
- **[erdosproblems.com/175](https://www.erdosproblems.com/175)**: `formally solved`

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

Check the current status on erdosproblems.com/175, then inspect the `@[category research ...]` annotation in `FormalConjectures/ErdosProblems/175.lean`. Update the annotation if the external status confirms the repository is out of date, and verify that the recorded status matches the source.

Written by the indexing model from the issue text.