Fix several out of date references to 4g/5g/6g/8g/9g.

Change-Id: Ifb8e4e13c7778a7c0113190051415e096f5db94f
Reviewed-on: https://go-review.googlesource.com/11390
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/test/cmp.go b/test/cmp.go
index 80d1bf6..6db9ce5 100644
--- a/test/cmp.go
+++ b/test/cmp.go
@@ -115,7 +115,7 @@
 	isfalse(ic != d)
 	isfalse(ie != e)
 
-	// 6g used to let this go through as true.
+	// gc used to let this go through as true.
 	var g uint64 = 123
 	var h int64 = 123
 	var ig interface{} = g