2013-12-type-params: fix error in example

Thanks to @lunny for pointing it out.

Change-Id: I159afe2fa49e18c3675b1af20fe942ad94dd3d09
Reviewed-on: https://go-review.googlesource.com/22089
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/design/15292/2013-12-type-params.md b/design/15292/2013-12-type-params.md
index 42cd3b7..832060f 100644
--- a/design/15292/2013-12-type-params.md
+++ b/design/15292/2013-12-type-params.md
@@ -364,10 +364,10 @@
 
 ```
 func [T] Sum(a, b T) T { return a + b }
-var v1 = Sum[int, int](0, 0)
-var v2 = Sum(0, 0)			// [int, int] deduced
+var v1 = Sum[int](0, 0)
+var v2 = Sum(0, 0)			// [int] deduced
 type [T] Cons struct { car, cdr T }
-var v3 = Cons{0, 0}			// [int, int] deduced
+var v3 = Cons{0, 0}			// [int] deduced
 type [T] Opaque T
 func [T] (a Opaque[T]) String() string {
 	return "opaque"