Fix ed-on-mnt4-753

[weikengchen]

Description

The current repo has two small issues regarding ed-on-mnt4-753

• we forgot to include it in the workspace Cargo.toml, so the CI never tested it, and cargo fmt never touched it.
• the curve parameters for ed-on-mnt4-753 was expressed as a mix of the old BigInt representation and the new field_new representation.

This PR fixes it, by including it in the workspace Cargo.toml as well as cleaning up the curve parameters.

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• Targeted PR against correct branch (master)
• Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Wrote unit tests
• Updated relevant documentation in the code
• Added a relevant changelog entry to the Pending section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer