cmd/gopherbot: fix misleading typo in cl2issue comment

The phrase "CL https://golang.org/issue/NNNN" does not make sense.
It was a typo in CL 39352 that implemented this functionality.
Also remove a stray trailing backslash introduced in CL 51116.

Change-Id: Ic1c9d1095c075cb6d9063a3d9e881df6b70414f0
Reviewed-on: https://go-review.googlesource.com/c/161458
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/cmd/gopherbot/gopherbot.go b/cmd/gopherbot/gopherbot.go
index 6f3c4bc..b2c6076 100644
--- a/cmd/gopherbot/gopherbot.go
+++ b/cmd/gopherbot/gopherbot.go
@@ -882,7 +882,7 @@
 
 }
 
-// cl2issue writes "Change https://golang.org/issue/NNNN mentions this issue"\
+// cl2issue writes "Change https://golang.org/cl/NNNN mentions this issue"
 // and the change summary on GitHub when a new Gerrit change references a GitHub issue.
 func (b *gopherbot) cl2issue(ctx context.Context) error {
 	monthAgo := time.Now().Add(-30 * 24 * time.Hour)