allow duplicate wpt designator on airway

[globin]

these actually exist, my assumption of that not being the case was wrong:

2024-09-01T15:57:50.456128Z  WARN vatsim_parser::airway: Duplicate for airway A411 and fix BNA
2024-09-01T15:57:50.471263Z  WARN vatsim_parser::airway: Duplicate for airway UN525 and fix CBA
2024-09-01T15:57:50.471343Z  WARN vatsim_parser::airway: Duplicate for airway W5 and fix CBA
2024-09-01T15:57:50.474126Z  WARN vatsim_parser::airway: Duplicate for airway W35 and fix CHG
2024-09-01T15:57:50.476214Z  WARN vatsim_parser::airway: Duplicate for airway W20 and fix CMA
2024-09-01T15:57:50.550398Z  WARN vatsim_parser::airway: Duplicate for airway L577 and fix GOSUL
2024-09-01T15:57:50.640241Z  WARN vatsim_parser::airway: Duplicate for airway W11 and fix MIA
2024-09-01T15:57:50.640261Z  WARN vatsim_parser::airway: Duplicate for airway W15 and fix MIA
2024-09-01T15:57:50.765363Z  WARN vatsim_parser::airway: Duplicate for airway W12 and fix SNT