design: 47781-parameterized-go-ast.md: fix a broken link

Change-Id: Ica74f0c8e51c5ba8346bf506166298b35ad9e872
GitHub-Last-Rev: 34c8e77a7ae4ee78d34dae780e528950b4589668
GitHub-Pull-Request: golang/proposal#34
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/343349
Reviewed-by: Robert Findley <rfindley@google.com>
diff --git a/design/47781-parameterized-go-ast.md b/design/47781-parameterized-go-ast.md
index ac470e2..ec07198 100644
--- a/design/47781-parameterized-go-ast.md
+++ b/design/47781-parameterized-go-ast.md
@@ -6,7 +6,7 @@
 
 ## Abstract
 
-This document proposes changes to `go/ast` to store the additional syntactic information necessary for the type parameters proposal ([#43651](golang.org/issues/43651)), including the amendment for type sets ([#45346](https://golang.org/issues/45346)). The changes to `go/types` related to type checking are discussed in a [separate proposal](https://golang.org/cl/328610).
+This document proposes changes to `go/ast` to store the additional syntactic information necessary for the type parameters proposal ([#43651](https://golang.org/issues/43651)), including the amendment for type sets ([#45346](https://golang.org/issues/45346)). The changes to `go/types` related to type checking are discussed in a [separate proposal](https://golang.org/cl/328610).
 
 ## Syntax Changes