Fix max depth description in XGBoost Estimator.

[nadiaya]

Issue #56 Fix max depth description in XGBoost Estimator.

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[codecov-io]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@ab3f16a). Click here to learn what that means. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #57   +/-   ##
=========================================
  Coverage          ?   92.22%           
=========================================
  Files             ?       52           
  Lines             ?     3113           
  Branches          ?       83           
=========================================
  Hits              ?     2871           
  Misses            ?      242           
  Partials          ?        0

Impacted Files	Coverage Δ
...er_pyspark/algorithms/XGBoostSageMakerEstimator.py	98.85% <ø> (ø)

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