Fix Spelling Error

[TJKoury]

_removeDefaultDataSoureListener - > _removeDefaultDataSourceListener

[cesium-concierge]

Thank you so much for the pull request @TJKoury! I noticed this is your first pull request and I wanted to say welcome to the Cesium community!

The Pull Request Guidelines is a handy reference for making sure your PR gets accepted quickly, so make sure to skim that.

• ❌ Missing CONTRIBUTORS.md entry.
  • Please add yourself to the contributors file!
• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[hpinkos]

Thanks @TJKoury! If you search for Soure, the same spelling mistake is in a few other places in that file. Can you fix that too please?

[TJKoury]

@hpinkos Good catch! Done.

[cesium-concierge]

Thanks again for your contribution @TJKoury!

No one has commented on this pull request in 30 days. Maintainers, can you review, merge or close to keep things tidy?

I'm going to re-bump this in 30 days. If you'd like me to stop, just comment with @cesium-concierge stop. If you want me to start again, just delete the comment.

[hpinkos]

whoops, sorry for the delay on this @TJKoury! I'll get this merged as soon as CI passes

[TJKoury]

You are doing me the favor, @hpinkos! Thanks for the update.