Notice of Filing of Proposed Rule Change by the Municipal Securities Rulemaking Board Consisting of Amendments to MSRB Rule G-20 (Gifts and Gratuities) and Related Amendments to MSRB Rule G-8 (Books and Records) and MSRB Rule G-9 (Preservation of Records), and To Clarify That Certain Interpretations by the Financial Industry Regulatory Authority and the National Association of Securities Dealers Would Be Applicable to Municipal Advisors