Remove filtering subway predictions by route

[PaulJKim]

Summary of changes

Asana Ticket: Investigate removing route-based filtering for predictions

This logic uses the routes fields in the source config for a stop to filter out predictions. This has caused a few instances, most recently for the new GLX stops, where trains that are being predicted in the feed do not show up on countdown clocks because the prediction is technically for a different route. A more specific example is an occasional Green Line B, C, or D train going up to Medford Tufts but not showing up on the countdown clocks because those signs source configs only had Green-E in the routes field.

In cases where there are multiple routes serving a station, there are always separate platform stop_ids that are used for each route (or route(s) for Green Line). JFK/UMass could be a potential special case but again, all platforms at that station have distinct platform stop_ids. Therefore, it should be safe and preferable to remove this filtering logic.

In addition, the historical context of this logic is that it was added to handle splitting out B and C/D predictions at Kenmore when the platform stop_ids were shared. Now we have distinct ones for the Kenmore B platforms so that further supports that we can safely remove the filtering logic #166

Testing done:

• Deployed temporary logging for when predictions are filtered out by route and there were zero instances a week

[github-actions]

Coverage of commit 44e0783

Summary coverage rate:
  lines......: 76.4% (1784 of 2334 lines)
  functions..: 76.4% (491 of 643 functions)
  branches...: no data found

Files changed coverage rate:
                                                             |Lines       |Functions  |Branches    
  Filename                                                   |Rate     Num|Rate    Num|Rate     Num
  =================================================================================================
  lib/signs/realtime.ex                                      |95.6%     45|90.9%    11|    -      0
  lib/signs/utilities/source_config.ex                       |95.7%     23| 100%     8|    -      0

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[jzimbel-mbta]

Thanks for the detailed explanation in the PR description! Looks good to me.