Remove unused option to change timezone

[freddidierRTE]

Considering

• The option to change timezone is not used today
• There s no plan for end users to use it
• This feature is complex to maintain/test
• To be fully functionnal , opfab would need to evolve to
  • have agenda feature compatible with it, taking into account that the agenda library is not natively compatible with time zone on community edition
  • permit access to the chosen timezone inside templates
• If the user wants to be in another time zone , depending on use cases , other more robust possibilities exist :
  • Change the OS TimeZone
  • Change the browser timezone via plugin ( for example : https://chrome.google.com/webstore/detail/change-timezone-for-googl/cejckpjfigehbeecbbfhangbknpidcnh?hl=fr )

It's so proposed to remove the feature