Rename GtfsPickupDropOff.ALLOWED to GtfsPickupDropOff.REGULAR

[qcdyx]

It's confusing that the regular pickup or dropoff enum value is ALLOWED when with this new rule it's actually not allowed.
 We can rename the enum value to REGULAR instead of ALLOWED. Looking at the GTFS reference, we have this for pickup_type. drop_off_type is similar:
Indicates pickup method. Valid options are:
0 or empty - Regularly scheduled pickup.
1 - No pickup available.
2 - Must phone agency to arrange pickup.
3 - Must coordinate with driver to arrange pickup.

which more in line with having a REGULAR enum value.