Update AlgoliaUnreachableHostException to OperationTimeout

- Algolia Client Version: 2.5.0 (I see that 3.0 was released 3 days ago, not sure if that resolves this)
- Language Version: Python 3.9.7

### Description

Client throws `algoliasearch.exceptions.AlgoliaUnreachableHostException`: Unreachable hosts during `replace_all_objects` operation. The issue was not that hosts were unreachable but that the operation was timing out. I fixed the problem by setting `readTimeout` to 100:

```
client = SearchClient.create(algolia_application_id, algolia_api_key)
index = client.init_index(algolia_index)
request_options = {
"readTimeout": 100
}
index.replace_all_objects(records, request_options)
```

A timeout should produce a timeout error. Unreachable is misleading.

### Steps To Reproduce

See description.
Use `replace_all_objects` on a sufficiently big index. Mine was 6393 rows and 10+ columns some with significant text blocks.

Commencez par suivre la gestion du délai d’expiration de replace_all_objects dans le client Python et la façon dont elle associe les échecs à AlgoliaUnreachableHostException. Reproduisez l’opération avec un index suffisamment volumineux, puis vérifiez qu’un délai d’expiration de lecture signale OperationTimeout, tandis que les hôtes réellement inaccessibles signalent toujours l’exception de l’hôte.

Rédigé par le modèle d'indexation à partir du texte de l'issue.