Updated default_options in config.rs to capture the return value of [].map, eliminating a build-time warning.

src/config.rs

@@ -1582,6 +1582,7 @@ impl PeerConfig {
 
     fn default_options() -> HashMap<String, String> {
         let mut mp: HashMap<String, String> = Default::default();
+        let _ =
         [
             keys::OPTION_CODEC_PREFERENCE,
             keys::OPTION_CUSTOM_FPS,