snappy: switch defaultcc to golang-codereviews.

LGTM=dsymonds
R=dsymonds
CC=golang-codereviews
https://codereview.appspot.com/201180043

lib/codereview/codereview.cfg

@@ -1 +1 @@
-defaultcc: golang-dev@googlegroups.com
+defaultcc: golang-codereviews@googlegroups.com