Removes depracated Contract.eventFilter. Fixes #1028.

[Exef]

What was wrong?

Contract.eventFilter() method marked as deprecated and it should be removed in v5.
Related to Issue #1028

How was it fixed?

I removed the deprecated function, the test that used it and documentation about it.

Cute Animal Picture

[Exef]

Thank you, @dylanjw for fixing my errors.

Can you tell me, what have I done wrong with test fixture?

[dylanjw]

Thanks for contributing!

pytest fixtures can be parametrized, so that everytime a test uses that fixture, it is run with each parameter.

The fixture decorator @pytest.fixture(params=['v3', 'v4']) was passing both 'v3' and 'v4' values to return_filter_by_api. Because the 'v3' conditional was removed, in the case when 'v3' was passed the ValueError on this line 523f493#diff-e3a6abe3e92df49f9a94069e9a05f9e7L147 was being raised.

[pipermerriam]

@dylanjw before this is merged we'll need to get a legacy v4 branch created to allow merging of these new v5 only features into master (and then anything that is a bugfix needs to be backported to v4)

[dylanjw]

The https://github.com/ethereum/web3.py/tree/v4 branch is up to date with 4.7.1

[veox]

Slug is referenced elsewhere in the docs (via :ref:), which produces a warning.

Section below also referenced.