blog: update code sample in the "Generating code" article

Fixes golang/go#20720.

Change-Id: Iabeadddba92d6d51f873d817446eb79f20694be6
GitHub-Last-Rev: bd9501d806e08aff6cf230d1490fee14e2ba5e6f
GitHub-Pull-Request: golang/blog#20
Reviewed-on: https://go-review.googlesource.com/c/blog/+/167763
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/content/generate.article b/content/generate.article
index 2d46713..e848880 100644
--- a/content/generate.article
+++ b/content/generate.article
@@ -150,7 +150,7 @@
 
 	$ go generate
 	$ cat pill_string.go
-	// generated by stringer -type Pill pill.go; DO NOT EDIT
+	// Code generated by stringer -type Pill pill.go; DO NOT EDIT.
 	
 	package painkiller