[REVIEW] Updating docs, readme, and umap param tests for 0.19

[cjnolet]

No description provided.

[JohnZed]

@gpucibot merge

[codecov-io]

Codecov Report

Merging #3731 (f44469c) into branch-0.19 (fd9ec89) will increase coverage by 5.24%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.19    #3731      +/-   ##
===============================================
+ Coverage        80.70%   85.95%   +5.24%     
===============================================
  Files              227      225       -2     
  Lines            17615    16987     -628     
===============================================
+ Hits             14217    14601     +384     
+ Misses            3398     2386    -1012     

Flag	Coverage Δ
dask	48.96% <ø> (+3.97%)	⬆️
non-dask	77.79% <ø> (+4.88%)	⬆️

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Impacted Files	Coverage Δ
python/cuml/__init__.py	95.58% <ø> (+0.20%)	⬆️
...cuml/_thirdparty/sklearn/preprocessing/__init__.py	100.00% <ø> (ø)
...on/cuml/_thirdparty/sklearn/preprocessing/_data.py	67.22% <ø> (+4.10%)	⬆️
...hirdparty/sklearn/preprocessing/_discretization.py	83.33% <ø> (-0.88%)	⬇️
...l/_thirdparty/sklearn/preprocessing/_imputation.py	85.54% <ø> (+22.74%)	⬆️
python/cuml/_thirdparty/sklearn/utils/extmath.py	97.22% <ø> (+40.32%)	⬆️
...cuml/_thirdparty/sklearn/utils/skl_dependencies.py	79.54% <ø> (+25.62%)	⬆️
...thon/cuml/_thirdparty/sklearn/utils/sparsefuncs.py	90.90% <ø> (+48.32%)	⬆️
...ython/cuml/_thirdparty/sklearn/utils/validation.py	64.10% <ø> (+41.65%)	⬆️
python/cuml/benchmark/algorithms.py	94.38% <ø> (ø)
... and 166 more

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