Remove deprecated `Globe.terrainExaggeration` and `Globe.terrainExaggerationRelativeHeight`

[jjhembd]

After https://github.com/CesiumGS/cesium/pull/11655 is merged, the functionality of Globe.terrainExaggeration and Globe.terrainExaggerationRelativeHeight will be moved to Scene.verticalExaggeration and Scene.verticalExaggerationRelativeHeight. The old Globe properties should be removed after the usual deprecation period.

Along with the properties themselves and their related specs, the following should also be updated:

• The Terrain Exaggeration Sandcastle should be updated to use the new API
• The private flag Globe._terrainExaggerationChanged should be removed
• The updateFrameState function in Scene should be simplified to remove the check for the deprecated properties