Remove deprecated method one_hot_encoding

[isVoid]

This PR removes deprecated method one_hot_encoding and its test cases. There is a test case for generic indexed dataframe in one_hot_encoding that was not covered in get_dummies, this PR adds that coverage.

[codecov]

Codecov Report

Merging #9977 (fc0fa93) into branch-22.02 (967a333) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@               Coverage Diff                @@
##           branch-22.02    #9977      +/-   ##
================================================
- Coverage         10.49%   10.43%   -0.06%     
================================================
  Files               119      119              
  Lines             20305    20448     +143     
================================================
+ Hits               2130     2134       +4     
- Misses            18175    18314     +139     

Impacted Files	Coverage Δ
python/dask_cudf/dask_cudf/sorting.py	92.30% <0.00%> (-0.61%)	⬇️
python/cudf/cudf/__init__.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/frame.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/index.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/parquet.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/series.py	0.00% <0.00%> (ø)
python/cudf/cudf/utils/utils.py	0.00% <0.00%> (ø)
python/cudf/cudf/utils/dtypes.py	0.00% <0.00%> (ø)
python/cudf/cudf/utils/ioutils.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/dataframe.py	0.00% <0.00%> (ø)
... and 15 more

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[galipremsagar]

@gpucibot merge