pyln-proto: upgrade coincurve

[nepet]

This upgrade includes https://github.com/ofek/coincurve/pull/188 which fix an issue with a license file during installation on some systems. This issue caused the FreeBSD tests to fail. Resolves #8579

There is no published version that includes the relevant commit yet, hence why this is pinned to a certain commit. We may upgrade to a new version once this has been included.

Changelog-None

[!IMPORTANT]

25.12 FREEZE October 27th: Non-bugfix PRs not ready by this date will wait for 26.03.

RC1 is scheduled on November 10th

The final release is scheduled for December 1st.

Checklist

Before submitting the PR, ensure the following tasks are completed. If an item is not applicable to your PR, please mark it as checked:

• [x] The changelog has been updated in the relevant commit(s) according to the guidelines.
• [ ] Tests have been added or modified to reflect the changes.
• [ ] Documentation has been reviewed and updated as needed.
• [x] Related issues have been listed and linked, including any that this PR closes.

[madelinevibes]

I suspect this was lost because it wasn't attached to an issue. Waiting to hear back from @nepet if the PR can be closed :( sorry about all of the double work