fix fs import

Author: arik-so

lightning-rapid-gossip-sync/src/processing.rs

@@ -391,7 +391,6 @@ impl<NG: Deref<Target=NetworkGraph<L>>, L: Deref> RapidGossipSync<NG, L> where L
 
 #[cfg(test)]
 mod tests {
-	use std::fs;
 	use bitcoin::Network;
 
 	#[cfg(feature = "std")]