Simplify simple-linked-list stub (#173)

exercises/practice/simple-linked-list/simple-linked-list.arr

@@ -2,29 +2,6 @@ use context essentials2020
 
 provide-types *
 
-#|
-  We have given you a beginning structure to help pass the tests here. 
-|#
 data LinkedList:
-  | empty-list
-  | linked-list(head, tail) with:
-    method get-head(self):
-      raise("please implement the get-head method")
-    end,
-    method get-tail(self):
-      raise("please implement the get-tail method")
-    end
-sharing:
-  method length(self):
-    raise("please implement the length method")
-  end,
-  method push(self, val):
-    raise("please implement the push method")
-  end,
-  method reversed(self):
-    raise("please implement the reversed method")
-  end,
-  method to-list(self):
-    raise("please implement the to-list method")
-  end
+  ... # Replace the dots with your implementation
 end