fix: death informant phone number error message

[jamil314]

Description

Fixes: opencrvs/opencrvs-core#10647

Checklist

• I have linked the correct Github issue under "Development"
• I have tested the changes locally, and written appropriate tests
• I have tested beyond the happy path (e.g. edge cases, failure paths)
• I have updated the changelog with this change (if applicable)
• I have updated the GitHub issue status accordingly

[github-actions]

Oops! Looks like you forgot to update the changelog. When updating CHANGELOG.md, please consider the following:

• Changelog is read by country implementors who might not always be familiar with all technical details of OpenCRVS. Keep language high-level, user friendly and avoid technical references to internals.
• Answer "What's new?", "Why was the change made?" and "Why should I care?" for each change.
• If it's a breaking change, include a migration guide answering "What do I need to do to upgrade?".