Remove object from NSLog and add prompt to enable AppAuthRequestTrace

[mattio]

Addresses #519 to remove the object from 2 NSLog statements and instead prompts developers to enable AppAuthRequestTrace to view the details.

[codecov-commenter]

Codecov Report

Merging #546 into master will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #546      +/-   ##
==========================================
- Coverage   83.75%   83.70%   -0.06%     
==========================================
  Files          50       50              
  Lines        4617     4620       +3     
==========================================
  Hits         3867     3867              
- Misses        750      753       +3     

Impacted Files	Coverage Δ
Source/AppAuthCore/OIDAuthState.m	46.71% <0.00%> (-0.31%)	⬇️
Source/AppAuthCore/OIDIDToken.m	88.09% <0.00%> (-1.07%)	⬇️

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