Remove deprecated method DataFrame.hash_columns.

[bdice]

This PR removes the deprecated method DataFrame.hash_columns. Users can replace existing calls like df.hash_columns(columns, method) with df[columns].hash_values(method). Resolves #9503, follows up on #9458.

[codecov]

Codecov Report

Merging #9943 (c0cd84d) into branch-22.02 (04f4219) will increase coverage by 0.03%.
The diff coverage is n/a.

❗ Current head c0cd84d differs from pull request most recent head 006ac25. Consider uploading reports for the commit 006ac25 to get more accurate results

@@               Coverage Diff                @@
##           branch-22.02    #9943      +/-   ##
================================================
+ Coverage         10.37%   10.41%   +0.03%     
================================================
  Files               119      119              
  Lines             20111    20499     +388     
================================================
+ Hits               2086     2134      +48     
- Misses            18025    18365     +340     

Impacted Files	Coverage Δ
python/cudf/cudf/core/dataframe.py	0.00% <ø> (ø)
python/cudf/cudf/io/hdf.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/orc.py	0.00% <0.00%> (ø)
python/cudf/cudf/_version.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/abc.py	0.00% <0.00%> (ø)
python/cudf/cudf/api/types.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/dlpack.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/feather.py	0.00% <0.00%> (ø)
... and 51 more

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[brandon-b-miller]

LGTM

[bdice]

This is a straightforward removal of code, so I'm going to merge with one approval.

@gpucibot merge

[bdice]

@gpucibot merge