no unusued vars

exercises/084_async.zig

@@ -46,6 +46,8 @@
 const print = @import("std").debug.print;
 
 pub fn main() void {
+    // Additional Hint: you can assign things to '_' when you
+    // don't intend to do anything with them.
     foo();
 }
 

patches/patches/084_async.patch

@@ -1,4 +1,4 @@
-49c49
+51c51
 <     foo();
 ---
->     var foo_frame = async foo();
+>     _ = async foo();