[REVIEW] Remove duplicate definitions from docs

[devavret]

Uses @copydoc to remove duplicate definitions from detail headers.
Depends on #5049
Also Closes #4528

[GPUtester]

Please update the changelog in order to start CI tests.

View the gpuCI docs here.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (branch-0.14@8bdcba3). Click here to learn what that means.
The diff coverage is n/a.

@@              Coverage Diff               @@
##             branch-0.14    #5069   +/-   ##
==============================================
  Coverage               ?   88.38%           
==============================================
  Files                  ?       55           
  Lines                  ?    10489           
  Branches               ?        0           
==============================================
  Hits                   ?     9271           
  Misses                 ?     1218           
  Partials               ?        0           

Impacted Files	Coverage Δ
python/cudf/cudf/_lib/legacy/__init__.py	100.00% <0.00%> (ø)
python/cudf/cudf/core/column/column.py	86.52% <0.00%> (ø)
python/cudf/cudf/core/dataframe.py	89.51% <0.00%> (ø)
python/cudf/cudf/utils/applyutils.py	98.73% <0.00%> (ø)
python/cudf/cudf/utils/docutils.py	100.00% <0.00%> (ø)
python/cudf/cudf/datasets.py	96.55% <0.00%> (ø)
python/cudf/cudf/io/dlpack.py	95.00% <0.00%> (ø)
python/cudf/cudf/core/series.py	89.70% <0.00%> (ø)
python/dask_cudf/dask_cudf/sorting.py	94.11% <0.00%> (ø)
python/dask_cudf/dask_cudf/io/tests/test_s3.py	95.65% <0.00%> (ø)
... and 45 more

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[davidwendt]

Looks good. Just some minor spelling, indenting requests.

[harrism]

rerun tests