Python example failing

[ibhati]

When running the Python example, I get the following assertion error:

~/ScalableVectorSearch$ python examples/python/example_vamana.py
Recall = 0.817
Traceback (most recent call last):
  File "/raid6/ishwarsi/projects/ScalableVectorSearch/examples/python/example_vamana.py", line 245, in <module>
    run()
  File "/raid6/ishwarsi/projects/ScalableVectorSearch/examples/python/example_vamana.py", line 162, in run
    assert(recall == 0.8288)
           ^^^^^^^^^^^^^^^^
AssertionError

This is probably introduced with #96 when the default parameters are added. We need to add some error margins.
Better to include running these examples in the CI with public repos.