Remark on changing order of (m + n) to (n + m) in drop' in Section 6.3 (#88)

* remarked on changing order of (m + n) to (n + m) in drop'

* trying to fix drop' duplication error

* it's actually the second xs

* trying to fix markdown error

* changed quote to backticks and repl

Author: Liable5607

src/Tutorial/Dependent.md

@@ -709,6 +709,15 @@ drop' 0     xs        = xs
 drop' (S k) (_ :: xs) = drop' k xs
 ```
 
+Note that changing the order from `(m + n)` to `(n + m)`
+in the second parameter will cause an error at the second `xs`:
+
+```repl
+While processing right hand side of drop'. Can't solve constraint between: plus n 0 and n.
+```
+
+You will learn why in the next section.
+
 ### Limitations
 
 After all the examples and exercises in this section