M365 Planner Timeline Fix to Asset Image URL in sample.json

[Billbrockbank]

• New sample
• Bug fix/update
• Related issues: fixes #X, partially #Y, mentioned in #Z

What's in this Pull Request?

Fix to the image URL in sample.json

Node Version

Node version used: v18.20.3

Checklist

• My pull request affects only ONE sample.
• My sample builds without any warnings
• I have updated the README.md file's Version history. For new samples, created a new README.md file matching this template
• My README.md has at least one static high-resolution screenshot (i.e. not a GIF) located in the assets folder.
• My README.md contains complete setup instructions, including pre-requisites and permissions required
• My solution includes a .nvmrc file indicating the version of Node.js

Submitter Guidance (DELETE AFTER READING)

The sample gallery does not render the image from the sample.json file. I have update the URL to fix.

[github-actions]

Sample PR validation for #5430

⚠️ Validation status: warnings

We automatically validate all pull requests against our contribution guidance to ensure that all samples provide a consistent experience to our community.

In order to merge this PR in a timely manner, the following criteria must be met:

Validation	Status
Pull request affects only one folder	✅ Succeeded
Sample folder name follows naming convention	✅ Succeeded
Sample requires a .nvmrc file	⚠️ Warning
Sample requires a README.md	⚠️ Warning
Sample requires a screenshot .png in assets folder	⚠️ Warning
No .sppkg file	✅ Succeeded
No node_modules folder	✅ Succeeded
No lib folder	✅ Succeeded

@Billbrockbank please address the above issues and push new changes to this branch.
For more information, see the contribution guidance.

[hugoabernier]

@Billbrockbank I see that your PR is still in draft. Let me know when we can process your PR.