remove types related to deprecated EthPM

[reedsa]

What was wrong?

Re-removal of EthPM types, done in https://github.com/ethereum/eth-typing/pull/60 but was reverted in https://github.com/ethereum/eth-typing/pull/64.

How was it fixed?

Removal of types, preserving URI for use elsewhere.

This change will require a major release version.

Todo:

• [X] Clean up commit history

• [X] Add or update documentation related to these changes

• [X] Add entry to the release notes

Cute Animal Picture

[fselmo]

I don't think this closes #75 though, right? We still need to remove the older ABI classes that are marked as @deprecated.

[reedsa]

@fselmo Linked to that by mistake, just got PR #82 up to close out #75.