Fix warnings in test_stats.py

[vyasr]

Description

Contributes to #9999 and #10363.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[codecov]

Codecov Report

Base: 88.37% // Head: 88.35% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (1776a53) compared to base (a9f9958).
Patch coverage: 84.00% of modified lines in pull request are covered.

Additional details and impacted files

@@               Coverage Diff                @@
##           branch-23.02   #12293      +/-   ##
================================================
- Coverage         88.37%   88.35%   -0.02%     
================================================
  Files               137      137              
  Lines             22657    22664       +7     
================================================
+ Hits              20022    20025       +3     
- Misses             2635     2639       +4     

Impacted Files	Coverage Δ
python/cudf/cudf/core/column/column.py	87.95% <ø> (-0.03%)	⬇️
python/cudf/cudf/core/series.py	95.83% <ø> (ø)
python/cudf/cudf/core/dataframe.py	93.49% <66.66%> (-0.18%)	⬇️
python/cudf/cudf/core/_base_index.py	81.15% <100.00%> (ø)
python/cudf/cudf/core/index.py	92.92% <100.00%> (ø)
python/cudf/cudf/testing/_utils.py	94.30% <100.00%> (+0.18%)	⬆️

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[vyasr]

rerun tests

[vyasr]

@gpucibot merge