Add "DO NOT EDIT" with static_code_generator

See convention golang/go#13560 (comment) for details.

Author: breml

bootstrap/cmd/static_code_generator/main.go

@@ -13,8 +13,7 @@ import (
 const (
 	delimiter = "// IMPORTANT: All code below this line is added to the parser as static code"
 
-	header = `// This file is automatically generated by go generate
-// Do not modify manually
+	header = `// Code generated by static_code_generator with go generate; DO NOT EDIT.
 
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