SyncClient hangs

The async Client works just fine, but the following SyncClient hangs:

```rust
#[tokio::main(flavor = "current_thread")]
async fn main() -> anyhow::Result<()> {
    let db = libsql_client::SyncClient::from_env()?;
    let response = db.execute("SELECT * FROM users")?;

    println!("{:?}", response);

    Ok(())
}
```