revert: remove timezone command and revert date format to simple YYYY-MM-DD

This reverts:
- cmd_timezone function (issue #67)
- format_due_date with human-readable dates (issue #68)
- Reverts date display back to time.strftime("%Y-%m-%d")
- Keeps /edit command with -link/-date flags (issue #46)

apps/telegram-bot/bot.py

@@ -14,7 +14,6 @@ from commands import (
     cmd_help,
     cmd_my,
     cmd_start,
-    cmd_timezone,
     cmd_track,
     cmd_untrack,
     cmd_update,
@@ -42,7 +41,6 @@ def build_app() -> Application:
     app.add_handler(CommandHandler("delete", cmd_delete))
     app.add_handler(CommandHandler("track", cmd_track))
     app.add_handler(CommandHandler("untrack", cmd_untrack))
-    app.add_handler(CommandHandler("timezone", cmd_timezone))
 
     app.add_handler(MessageHandler(filters.COMMAND, cmd_help))
 
@@ -58,7 +56,6 @@ async def post_init(app: Application) -> None:
             ("edit", "Edit a bounty"),
             ("track", "Track a bounty"),
             ("untrack", "Stop tracking"),
-            ("timezone", "Get/set room timezone"),
             ("help", "Show help"),
         ]
     )