chore(Store.Predictions): Add log when record removed for debugging

[KaylaBrady]

Summary

Ticket: In support of Predictions crash due to missing trip

What is this PR for?

One possible reason that clients are experiencing missing trips is that the trip could be removed from the ETS store prematurely. By logging when trips & predictions are removed from the store, we can better understand if trips are removed before their corresponding predictions in the backend or if this is a frontend issue.

[github-actions]

Coverage of commit eb11d05

Summary coverage rate:
  lines......: 79.7% (1364 of 1711 lines)
  functions..: 69.6% (569 of 817 functions)
  branches...: no data found

Files changed coverage rate:
                                                                         |Lines       |Functions  |Branches    
  Filename                                                               |Rate     Num|Rate    Num|Rate     Num
  =============================================================================================================
  lib/mbta_v3_api/store/predictions.ex                                   |98.4%     62| 100%    13|    -      0

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