Drop no longer used count models

[rowanseymour]

DROP TABLE "notifications_notificationcount";
DROP TABLE "tickets_ticketcount";

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (23df4e7) to head (e79c76b).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #5615   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          560       562    +2     
  Lines        25793     25786    -7     
=========================================
- Hits         25793     25786    -7     

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