Fix typo in Toy tutorial Ch1

[xgupta]

I guess this revision should be close, changes are not correct.

mlir/docs/Tutorials/Toy/Ch-1.md

def main() {
   var c = multiply_transpose(a, b);
 
   # A second call to `multiply_transpose` with <2, 3> for both arguments will
   # reuse the previously specialized and inferred version and return <3, 2>.
   var d = multiply_transpose(b, a);
 
   # A new call with <3, 2> (instead of <2, 3>) for both dimensions will
   # trigger another specialization of `multiply_transpose`.
-  var e = multiply_transpose(c, d);
+  var e = multiply_transpose(b, c);
 
   # Finally, calling into `multiply_transpose` with incompatible shape will
   # trigger a shape inference error.
   var f = multiply_transpose(transpose(a), c);
 }
 ```
 
 ## The AST