Increase deprecation level to warning

[OptimumCode]

Resolves #228

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.69%. Comparing base (027c709) to head (89520e2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...mumcode/json/schema/extension/ExternalAssertion.kt	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #252      +/-   ##
==========================================
+ Coverage   90.55%   90.69%   +0.13%     
==========================================
  Files         133      133              
  Lines        3983     3977       -6     
  Branches     1059     1058       -1     
==========================================
  Hits         3607     3607              
+ Misses         82       76       -6     
  Partials      294      294              

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