language_models: Remove unnecessary LM Studio connection refused log (#37277)

In zed logs you can see these logs of lmstudio connection refused.
Currently zed connects to lmstudio by default as there is no credential
mechanism to check if the user has enabled lmstudio previously or not
like we do with other providers using api keys.

This pr removes the below annoying log and makes the zed logs less
polluted.

```
2025-09-01T02:11:33+05:30 ERROR [language_models] Other(error sending request for url (http://localhost:1234/api/v0/models)

Caused by:
    0: client error (Connect)
    1: tcp connect error: Connection refused (os error 61)
    2: Connection refused (os error 61))
```

Release Notes:

- N/A

---------

Signed-off-by: Umesh Yadav <git@umesh.dev>

crates/language_model/src/language_model.rs

@@ -681,6 +681,8 @@ pub trait LanguageModelTool: 'static + DeserializeOwned + JsonSchema {
 /// An error that occurred when trying to authenticate the language model provider.
 #[derive(Debug, Error)]
 pub enum AuthenticateError {
+    #[error("connection refused")]
+    ConnectionRefused,
     #[error("credentials not found")]
     CredentialsNotFound,
     #[error(transparent)]