go/types: remove a stale comment

Clean up a comment that was deleted in types2 in CL 353135.

Change-Id: If339efa133e2a3d1eaa3b1e69458471677018261
Reviewed-on: https://go-review.googlesource.com/c/go/+/358517
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/src/go/types/typestring.go b/src/go/types/typestring.go
index 2feaf62..9154ebc 100644
--- a/src/go/types/typestring.go
+++ b/src/go/types/typestring.go
@@ -275,9 +275,6 @@
 			break
 		}
 		// Optionally write out package for typeparams (like Named).
-		// TODO(danscales): this is required for import/export, so
-		// we maybe need a separate function that won't be changed
-		// for debugging purposes.
 		if t.obj.pkg != nil {
 			writePackage(w.buf, t.obj.pkg, w.qf)
 		}