Refactor main.py: Remove asyncio and modify retry_on_failure function

[albertkun]

This pull request refactors the main.py file by removing the asyncio module and modifying the retry_on_failure function. The changes include removing the run_coroutine function and updating the retry_on_failure function to directly call the gtfs_rt_helper.update_gtfs_realtime_data function. This improves the code readability and simplifies the logic.