Fix documentation of KMeans

[lowener]

Just a small fix of duplicates in KMeans doc.

[dantegd]

lgtm

[dantegd]

@gpucibot merge

[codecov-io]

Codecov Report

Merging #3595 (4b38b4f) into branch-0.19 (fd9ec89) will increase coverage by 0.12%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.19    #3595      +/-   ##
===============================================
+ Coverage        80.70%   80.83%   +0.12%     
===============================================
  Files              227      227              
  Lines            17615    17737     +122     
===============================================
+ Hits             14217    14337     +120     
- Misses            3398     3400       +2     

Flag	Coverage Δ
dask	45.30% <ø> (+0.31%)	⬆️
non-dask	73.09% <ø> (+0.17%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
python/cuml/cluster/kmeans.pyx	91.95% <ø> (ø)
python/cuml/dask/solvers/cd.py	100.00% <0.00%> (ø)
python/cuml/common/numba_utils.py	0.00% <0.00%> (ø)
python/cuml/internals/global_settings.py	100.00% <0.00%> (ø)
python/cuml/dask/preprocessing/encoders.py	100.00% <0.00%> (ø)
python/cuml/metrics/_ranking.py	98.57% <0.00%> (+0.02%)	⬆️
python/cuml/preprocessing/encoders.py	95.10% <0.00%> (+0.02%)	⬆️
python/cuml/common/array_descriptor.py	98.24% <0.00%> (+0.03%)	⬆️
python/cuml/common/array.py	96.99% <0.00%> (+0.04%)	⬆️
python/cuml/dask/common/dask_arr_utils.py	95.83% <0.00%> (+0.05%)	⬆️
... and 34 more

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