chore: remove signals from unserializable list

[BryanttV]

Description

This PR removes some signals from unserializable list according to the added support for complex types in this PR.

Supporting information

• feat: add support for complex types in dicts and lists #483 (Merge this first)
• Add support for complex types in dictionaries and lists #441

Deadline

None

Checklists

Check off if complete or not applicable:

Merge Checklist:

• All reviewers approved
• Reviewer tested the code following the testing instructions
• CI build is green
• Version bumped
• Changelog record added with short description of the change and current date
• Documentation updated (not only docstrings)
• Integration with other services reviewed
• Fixup commits are squashed away
• Unit tests added/updated
• Noted any: Concerns, dependencies, migration issues, deadlines, tickets

Post Merge:

• Create a tag
• Create a release on GitHub
• Check new version is pushed to PyPI after tag-triggered build is
  finished.
• Delete working branch (if not needed anymore)
• Upgrade the package in the Open edX platform requirements (if applicable)

[openedx-webhooks]

Thanks for the pull request, @BryanttV!

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