Method References: Fix doDrum call in lambda (#115)

Co-authored-by: Ethan McCue <[email protected]>

Author: Maia-Everett

src/lambdas/method_references.md

@@ -17,7 +17,7 @@ class Main {
     }
 
     void main() {
-        Drummer drummer = () -> drum();
+        Drummer drummer = () -> doDrum();
         drummer.drum();
     }
 }