Use Datasets API to Update Docstring Examples

[oorliu]

closes #2361

Docstring examples now use the new method of creating graphs by using the datasets API. This change cleans up the code by eliminating the usage of cuDF.

Old docstring example:

>>> M = cudf.read_csv(datasets_path / 'karate.csv', delimiter=' ',
...                   dtype=['int32', 'int32', 'float32'], header=None)
>>> G = cugraph.Graph()
>>> G.from_cudf_edgelist(M, source='0', destination='1')

Updated docstring example:

>>> from cugraph.experimental.datasets import karate
>>> G = karate.get_graph()

[codecov-commenter]

Codecov Report

Merging #2441 (9d8a302) into branch-22.08 (2a57740) will increase coverage by 0.04%.
The diff coverage is 83.72%.

❗ Current head 9d8a302 differs from pull request most recent head 9ade9a2. Consider uploading reports for the commit 9ade9a2 to get more accurate results

@@               Coverage Diff                @@
##           branch-22.08    #2441      +/-   ##
================================================
+ Coverage         61.19%   61.23%   +0.04%     
================================================
  Files               106      106              
  Lines              5553     5572      +19     
================================================
+ Hits               3398     3412      +14     
- Misses             2155     2160       +5     

Impacted Files	Coverage Δ
...graph/cugraph/centrality/betweenness_centrality.py	89.65% <ø> (ø)
...on/cugraph/cugraph/centrality/degree_centrality.py	81.81% <ø> (ø)
...graph/cugraph/centrality/eigenvector_centrality.py	93.93% <ø> (ø)
...thon/cugraph/cugraph/centrality/katz_centrality.py	89.13% <ø> (ø)
python/cugraph/cugraph/community/ecg.py	100.00% <ø> (ø)
python/cugraph/cugraph/community/egonet.py	94.73% <ø> (-2.64%)	⬇️
...ython/cugraph/cugraph/community/ktruss_subgraph.py	85.29% <ø> (ø)
python/cugraph/cugraph/community/leiden.py	100.00% <ø> (ø)
python/cugraph/cugraph/community/louvain.py	100.00% <ø> (ø)
...n/cugraph/cugraph/community/spectral_clustering.py	79.66% <ø> (ø)
... and 28 more

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[rlratzel]

I only see an update to bfs.py in this PR. Shouldn't the other docstrings be updated the same way, or have they been updated elsewhere in another PR?

[rlratzel]

rerun tests

#2473 was merged which should resolve test failures.

[rlratzel]

@gpucibot merge