lib/codereview: fix doc/go1.*.txt exception

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/108950046

lib/codereview/codereview.py

@@ -1954,7 +1954,7 @@ def submit(ui, repo, *pats, **opts):
 	if cl.cc:
 		about += "CC=" + JoinComma([CutDomain(s) for s in cl.cc]) + "\n"
 
-	if not cl.reviewer:
+	if not cl.reviewer and needLGTM(cl):
 		raise hg_util.Abort("no reviewers listed in CL")
 
 	if not cl.local: