Remove log depth skin workaround

[baothientran]

Fixes #6447
Fixes #6416

I tested it using model miner.glb (#8875) and bear_on_balloon.gltf (#6416)

[cesium-concierge]

Thanks for the pull request @baothientran!

• ✔️ Signed CLA found.
• ❔ 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.

[lilleyse]

One of the model unit tests was failing locally. This is because we still have glTF 1.0 versions of CesiumMan in our tests and they have the unnormalized bone weights problem. In lieu of fixing the model which is complicated with glTF 1.0 I tweaked the test so that he faces the camera and the missing chunk doesn't overlap the center pixel.

For reference, this is the issue recreated in a local sandcastle:

[lilleyse]

Thanks for the fix @baothientran, and as a result some nice code cleanup!