misc/nacl: exclude cmd/link from the test zip.

It does not appear to be necessary, and cmd/link does not appear in release branches.

LGTM=rsc
R=adg, rsc
CC=golang-codereviews
https://golang.org/cl/176900044
diff --git a/misc/nacl/testzip.proto b/misc/nacl/testzip.proto
index fd0c6a0..07d4a1d 100644
--- a/misc/nacl/testzip.proto
+++ b/misc/nacl/testzip.proto
@@ -18,9 +18,6 @@
 				gofmt_test.go
 				testdata
 					+
-			link
-				testdata
-					+
 		archive
 			tar
 				testdata