Fix use double Endpoint -> SecretKey (#276)

Fix use double Endpoint -> SecretKey

src/app/docs/examples/gossip-chat/page.mdx

@@ -46,7 +46,7 @@ The first step is creating a basic endpoint configuration. Replace the following
 
 ```rust
 use anyhow::Result;
-use iroh::{Endpoint, Endpoint};
+use iroh::{Endpoint, SecretKey};
 
 #[tokio::main]
 async fn main() -> Result<()> {