Update outdated NASA GIBS documentation link in web-map-tile-service-with-time example

[hansi2007]

Description

Updates the outdated NASA GIBS documentation link in the web-map-tile-service-with-time Sandcastle example. The previous link is no longer maintained, so this change replaces it with the current GIBS API documentation.

Issue number and link

Fixes #12442

Testing plan

This is a documentation-only change and does not affect application behavior.

Verified that the updated documentation link is valid and resolves correctly.

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

AI acknowledgment

• I used AI to generate content in this PR
• If yes, I have reviewed the AI-generated content before submitting

If yes, I used the following Tool(s) and/or Service(s):

Claude

If yes, I used the following Model(s):

Claude Sonnet 5

[github-actions]

Thank you for the pull request, @hansi2007! Welcome to the Cesium community!

In order for us to review your PR, please complete the following steps:

• Send in a Contributor License Agreement (CLA)
• Add yourself to the contributors file

Review Pull Request Guidelines to make sure your PR gets accepted quickly.