Update One-Hot Encoder doc

[lowener]

Closes #3598.

[dantegd]

lgtm

[dantegd]

@gpucibot merge

[JohnZed]

Observed failure: ```
assert 0.7248901720406369 >= 0.99

• where 0.7248901720406369 = adjusted_rand_score(array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,\n 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,... 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,\n 2, 2, 2, 2, 2, 2, 2, 2, 2, 2], dtype=int32), array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,\n 0., 0., 0., 0., 0., 0., 0., 0., 0., ...., 4., 4., 4., 4., 4., 4., 4., 4.,\n 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4.],\n dtype=float32))
• where array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,\n 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,... 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,\n 2, 2, 2, 2, 2, 2, 2, 2, 2, 2], dtype=int32) = <function asnumpy at 0x7fa09c796700>(array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,\n 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,... 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,\n 2, 2, 2, 2, 2, 2, 2, 2, 2, 2], dtype=int32))

•  where <function asnumpy at 0x7fa09c796700> = cp.asnumpy
  

• and array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,\n 0., 0., 0., 0., 0., 0., 0., 0., 0., ...., 4., 4., 4., 4., 4., 4., 4., 4.,\n 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4.],\n dtype=float32) = <function asnumpy at 0x7fa09c796700>(array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,\n 0., 0., 0., 0., 0., 0., 0., 0., 0., ...., 4., 4., 4., 4., 4., 4., 4., 4.,\n 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4., 4.],\n dtype=float32))

•  where <function asnumpy at 0x7fa09c796700> = cp.asnumpy
  

https://gpuci.gpuopenanalytics.com/job/rapidsai/job/gpuci/job/cuml/job/prb/job/cuml-gpu-test/CUDA=11.0,GPU_LABEL=gpu-a100,OS=ubuntu18.04,PYTHON=3.8/764/testReport/junit/cuml.test/test_kmeans/test_kmeans_clusters_blobs_1_0_5_25_1000_/

[JohnZed]

rerun tests

[codecov-io]

Codecov Report

Merging #3600 (7c8ac1b) into branch-0.19 (fd9ec89) will increase coverage by 0.12%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.19    #3600      +/-   ##
===============================================
+ 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/preprocessing/encoders.py	95.10% <ø> (+0.02%)	⬆️
python/cuml/cluster/kmeans.pyx	91.95% <0.00%> (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/common/array_descriptor.py	98.24% <0.00%> (+0.03%)	⬆️
python/cuml/common/array.py	96.99% <0.00%> (+0.04%)	⬆️
... and 35 more

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