[BUG] Update some clustering algos to only support undirected graphs

[jnke2016]

Our current implementation of Louvain, Leiden, KTruss and Triangle Count only support undirected graphs. To enforce that, we are currently raising an exception if a graph is not of type Graph but this is ineffective if a user create a cugraph.Graph with the parameter directed=True

This PR

• Raises an exception if directed=True when creating a cugraph.Graph
• Update the docstrings for those algos
• Add tests

closes #2263

[codecov-commenter]

Codecov Report

Merging #2267 (3f1d7ef) into branch-22.06 (4a6263a) will decrease coverage by 40.09%.
The diff coverage is 0.00%.

@@                Coverage Diff                @@
##           branch-22.06    #2267       +/-   ##
=================================================
- Coverage         63.97%   23.87%   -40.10%     
=================================================
  Files               100      100               
  Lines              4436     4435        -1     
=================================================
- Hits               2838     1059     -1779     
- Misses             1598     3376     +1778     

Impacted Files	Coverage Δ
...ython/cugraph/cugraph/community/ktruss_subgraph.py	20.58% <0.00%> (-64.71%)	⬇️
python/cugraph/cugraph/community/leiden.py	25.00% <0.00%> (-67.31%)	⬇️
python/cugraph/cugraph/community/louvain.py	25.00% <0.00%> (-67.31%)	⬇️
python/cugraph/cugraph/community/triangle_count.py	37.50% <0.00%> (-51.39%)	⬇️
python/cugraph/cugraph/dask/community/louvain.py	24.24% <0.00%> (-1.57%)	⬇️
python/cugraph/cugraph/components/connectivity.py	13.33% <0.00%> (-81.67%)	⬇️
python/cugraph/cugraph/traversal/sssp.py	10.67% <0.00%> (-81.56%)	⬇️
python/cugraph/cugraph/structure/hypergraph.py	8.46% <0.00%> (-81.54%)	⬇️
...thon/cugraph/cugraph/centrality/katz_centrality.py	7.84% <0.00%> (-80.40%)	⬇️
python/cugraph/cugraph/link_analysis/pagerank.py	16.00% <0.00%> (-80.00%)	⬇️
... and 41 more

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[rlratzel]

Looks good, just a few minor requests.

[BradReesWork]

@gpucibot merge