fix: add missing await for mutationKeys in decodeSyncdMutations

When hkdf became async, mutationKeys also became async but the call
site wasn't updated. This caused Promise<Promise<Key>> instead of
Promise<Key>, breaking contact sync events (contacts.upsert).

Ref: WhiskeySockets/Baileys#2288

src/Utils/chat-utils.ts

@@ -264,7 +264,7 @@ export const decodeSyncdMutations = async (
 			})
 		}
 
-		return mutationKeys(keyEnc.keyData!)
+		return await mutationKeys(keyEnc.keyData!)
 	}
 }