Fix postUpdate spec

[anne-gropler]

Description

I noticed that there are 2 Scene specs that do the same, but have different descriptions. I guess this is just a copy paste error, that's why postUpdate was missing. I updated that test, and fixed a typo in the other test.

Issue number and link

Let me know if you need an issue for that, I didn't create one because it's neither a feature nor a bug, just fixing a test that I presume not to be doing what it should do.

Testing plan

I ran the tests using npm run test and it works.

Author checklist

• I have submitted a Contributor License Agreement yes, see fix #3674 #3675 (comment)
• I have added my name to CONTRIBUTORS.md
• [ ] I have updated CHANGES.md with a short summary of my change no, because it did not change the Cesium API
• I have added or updated unit tests to ensure consistent code coverage
• [ ] I have update the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[ggetz]

Great, thanks for catching this @anne-gropler! The fix works perfectly.