chore: Run rustfmt on exercises

exercises/structs/structs3.rs

@@ -17,7 +17,11 @@ impl Package {
         if weight_in_grams <= 0 {
             // Something goes here...
         } else {
-            return Package {sender_country, recipient_country, weight_in_grams};
+            return Package {
+                sender_country,
+                recipient_country,
+                weight_in_grams,
+            };
         }
     }