cmd/go: follow convention for generated code comment

Follow the convertion (https://golang.org/s/generatedcode) for generated
code in alldocs.go

Change-Id: I03985de20363ba8e09a5a624a931090ec8d196e6
Reviewed-on: https://go-review.googlesource.com/118816
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/alldocs.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// DO NOT EDIT THIS FILE. GENERATED BY mkalldocs.sh.
+// Code generated by mkalldocs.sh; DO NOT EDIT.
 // Edit the documentation in other files and rerun mkalldocs.sh to generate this one.
 
 // Go is a tool for managing Go source code.

src/cmd/go/internal/help/help.go

@@ -39,7 +39,7 @@ func Help(args []string) {
 		fmt.Println("// Use of this source code is governed by a BSD-style")
 		fmt.Println("// license that can be found in the LICENSE file.")
 		fmt.Println()
-		fmt.Println("// DO NOT EDIT THIS FILE. GENERATED BY mkalldocs.sh.")
+		fmt.Println("// Code generated by mkalldocs.sh; DO NOT EDIT.")
 		fmt.Println("// Edit the documentation in other files and rerun mkalldocs.sh to generate this one.")
 		fmt.Println()
 		buf := new(bytes.Buffer)