Remove caching for vehicle arrival times

[codecov[bot]]

Codecov Report

Merging #189 (29f6418) into main (5e68ff0) will increase coverage by 0.01%. The diff coverage is n/a.

:exclamation: Current head 29f6418 differs from pull request most recent head 4a87fec. Consider uploading reports for the commit 4a87fec to get more accurate results

@@            Coverage Diff             @@
##             main     #189      +/-   ##
==========================================
+ Coverage   94.53%   94.55%   +0.01%     
==========================================
  Files         118      118              
  Lines        4663     4661       -2     
==========================================
- Hits         4408     4407       -1     
+ Misses        255      254       -1     

Files Changed	Coverage Δ
conflowgen/domain_models/vehicle.py	98.33% <ø> (+1.55%)	:arrow_up:

[1kastner]

Also see https://github.com/domdfcoding/enum_tools/issues/77 for the pinned Sphinx version.