test/fixedbugs: fix typo in comment

Fix copy paste error pointed out by rsc, https://golang.org/cl/107290043/diff/60001/test/fixedbugs/issue8074.go#newcode7

LGTM=ruiu, r
R=golang-codereviews, ruiu, r
CC=golang-codereviews
https://golang.org/cl/106210047

test/fixedbugs/issue8074.go

@@ -4,7 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// issue 8073.
+// issue 8074.
 // was "cannot take the address of 1"
 
 package main