Bump gtfs-lib to 6.0.3

[landonreed]

Checklist

• Appropriate branch selected (all PRs must first be merged to dev before they can be merged to master)
• Any modified or new methods or classes have helpful JavaDoc and code is thoroughly commented
• The description lists all applicable issues this PR seeks to resolve
• The description lists any configuration setting(s) that differ from the default settings
• All tests and CI builds passing

Description

Fix #313. This includes a new gtfs-lib version with changes from conveyal/gtfs-lib#287

[codecov-commenter]

Codecov Report

Merging #315 into dev will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                dev     #315   +/-   ##
=========================================
  Coverage     19.93%   19.93%           
  Complexity      410      410           
=========================================
  Files           151      151           
  Lines          8328     8328           
  Branches       1155     1155           
=========================================
  Hits           1660     1660           
  Misses         6520     6520           
  Partials        148      148           

Flag	Coverage Δ	Complexity Δ
#unit_tests	19.93% <ø> (ø)	410.00 <ø> (ø)

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[landonreed]

🎉 This PR is included in version 3.7.0 🎉

The release is available on GitHub release

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