Update doc from DDLogLevelWarn to DDLogLevelWarning to match library

[l3ender]

New Pull Request Checklist

• I have read and understood the CONTRIBUTING guide
• I have read the Documentation
• I have searched for a similar pull request in the project and found none

• I have updated this branch with the latest master to avoid conflicts (via merge from master or rebase)
• I have added the required tests to prove the fix/feature I am adding
• I have updated the documentation (if necessary)
• I have run the tests and they pass
• I have run the lint and it passes (pod lib lint)

Pull Request Description

Fixes #1382.

[codecov]

Codecov Report

Merging #1383 (6455650) into master (590a4b2) will decrease coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1383      +/-   ##
==========================================
- Coverage   51.75%   51.66%   -0.09%     
==========================================
  Files          33       33              
  Lines        5725     5725              
  Branches      491      491              
==========================================
- Hits         2963     2958       -5     
- Misses       2578     2583       +5     
  Partials      184      184              

see 3 files with indirect coverage changes

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