Fix arrival count for SampleGTFSProvider
Fix arrival count for SampleGTFSProvider

I didn't audit frequencies.txt edge cases well enough initially... looks
like two arrivals for the CITY2 trip snuck in for their actual listed
arrival_time, while our code assumes that the arrival_time is only
relative to the start_time listed in frequencies.txt.

The two arrivals *correctly* removed in the new code:
('CITY', 'NANAA', <Arrow [2007-06-03T06:49:00-07:00]>)
('CITY', 'STAGECOACH', None, <Arrow [2007-06-03T06:56:00-07:00]>)

spaceboats/busbus