Resolves: #1910176
    Rebase to tzdata-2020f including changes for tzdata-2020e
    - tzdata-2020f fixes a bug in tzdata-2020e that caused an
      invalid zi file in rearguard format
    - Volgograd changes time zone from UTC+04 to UTC+03 on 2020-12-27.
    - Australia/Currie is identical to Australia/Hobart for all
      timestamps since 1970 and was therefore created by mistake,
      now moved to the "backward" file.