[#567] remove CHECKS file, as healhchecks were moved to app.json

[pnatashap]

fix for

Deprecated: Usage of the CHECKS file is deprecated in favor of healthchecks in app.jsonK
remote:  !     Please move your healthchecks to app.json.K

[pnatashap]

@yegor256 please take a look

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a090ab4) 34.92% compared to head (a5ab64c) 34.92%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #570   +/-   ##
=======================================
  Coverage   34.92%   34.92%           
=======================================
  Files          47       47           
  Lines        1300     1300           
=======================================
  Hits          454      454           
  Misses        846      846           

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