Remove rake tasks for managing the fixed closing date
Remove rake tasks for managing the fixed closing date

We might need these at the end of the next administration, but for now they reference ``Petition::FIXED_CLOSING_DATE`` which no longer exists so they have to go.

alphagov/e-petitions,joelanman/e-petitions,joelanman/e-petitions,oskarpearson/e-petitions,alphagov/e-petitions,StatesOfJersey/e-petitions,ansonK/e-petitions,unboxed/e-petitions,alphagov/e-petitions,StatesOfJersey/e-petitions,unboxed/e-petitions,joelanman/e-petitions,telekomatrix/e-petitions,oskarpearson/e-petitions,unboxed/e-petitions,ansonK/e-petitions,oskarpearson/e-petitions,alphagov/e-petitions,unboxed/e-petitions,telekomatrix/e-petitions,telekomatrix/e-petitions,StatesOfJersey/e-petitions,ansonK/e-petitions,StatesOfJersey/e-petitions