Remove invalid link to NSIDC resources

[yvonnefroehlich]

Description of proposed changes

Fixes #9075

Reminders

• Make sure that your code follows our style. Use the other functions/files as a basis.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Describe changes to function behavior and arguments in a comment below the function declaration.
• If adding new functionality, add a detailed description to the documentation and/or an example.

[Esteban82]

I think we should leave "Digital media. Accessed April 24, 2008." in the citation.