Release note about rust compiler unicode version

[alex-hunt-materialize]

Release note about rust compiler unicode version

Motivation

The linter told me to do this. I have no idea why any customer would care about this.

Verification

@def- Why do we need a release note for this?

[github-actions]

Thanks for opening this PR! Here are a few tips to help make the review process smooth for everyone.

PR title guidelines

• Use imperative mood: "Fix X" not "Fixed X" or "Fixes X"
• Be specific: "Fix panic in catalog sync when controller restarts" not "Fix bug" or "Update catalog code"
• Prefix with area if helpful: compute: , storage: , adapter: , sql:

Pre-merge checklist

• The PR title is descriptive and will make sense in the git log.
• This PR has adequate test coverage / QA involvement has been duly considered. (trigger-ci for additional test/nightly runs)
• If this PR includes major user-facing behavior changes, I have pinged the relevant PM to schedule a changelog post.
• This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• If this PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way), then it is tagged with a T-proto label.
• If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label (example).

[kay-kim]

FYI -- We have been auto-generating our relnotes each week. See https://materializeinc.slack.com/archives/CPNFV9CVB/p1775137892471919 (which has info about this week's release). So ... not sure which linter is asking you to do what or why 😄