Revert "requirements/deps upgrade raiden-contracts"

[karlb]

This reverts commit 77e8d6b.

Works around #5122.

PR review check list

Quality check list that cannot be automatically verified.

• Safety
  • The changes respect the necessary conditions for safety (https://raiden-network-specification.readthedocs.io/en/latest/smart_contracts.html#protocol-values-constraints)
• Code quality
  • Error conditions are handled
  • Exceptions are propagated to the correct parent greenlet
  • Exceptions are correctly classified as recoverable or unrecoverable
• Compatibility
  • State changes are forward compatible
  • Transport messages are backwards and forward compatible
• Commits
  • Have good messages
  • Squashed unecessary commits
• If it's a bug fix:
  • Regression test for the bug
    • Properly covers the bug
    • If an integration test is used, it could not be written as a unit test
• Documentation
  • A new CLI flag was introduced, is there documentation that explains usage?
• Specs
  • If this is a protocol change, are the specs updated accordingly? If so, please link PR from the specs repo.
• Is it a user facing feature/bug fix?
  • Changelog entry has been added

[palango]

Looks good to me.