Documentation made reference to an unknown entity "DisableHTMLEscaping,"
    but I think it actually meant the method "Encoder.SetEscapeHTML."

    Fixes #17255

Change-Id: I18fda76f8066110caef85fd33698de83d632e646
Reviewed-on: https://go-review.googlesource.com/29931Reviewed-by: Ian Lance Taylor <iant@golang.org>