Remove custom certificate handling

[diachenko-mischa]

Certificate validation logic implemented in the
Data SDK is a subject of transient errors, as
it is implemented on top of deprecated APIs.

Given that there's no handling of the custom
certificates and logic corresponds to the
default certificate handling in the iOS, custom
implementation can be removed in the faviour
of default handling.

Relates-To: HERESDK-5806

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.28%. Comparing base (e4fdb37) to head (52a0dbb).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1635      +/-   ##
==========================================
- Coverage   80.30%   80.28%   -0.01%     
==========================================
  Files         349      349              
  Lines       13952    13953       +1     
  Branches     1492     1493       +1     
==========================================
- Hits        11203    11202       -1     
- Misses       2148     2152       +4     
+ Partials      601      599       -2     

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