update prefab override documentation

[alexmontAmazon]

Change summary

Update the prefab override documentation to reflect new variable names and the switch from registry to cvar settings.

Submission Checklist:

• Descriptive active voice - Do descriptive sentences have a clear subject and action verb?
• Answer the question at hand - Does the documentation answer a what, why, how, or where type of question?
• Consistency - Does the content consistently follow the Style Guide?
• Help the user - Does the documentation show the user something meaningful?

[cgalvan]

It might be worth combining these into one section, because they aren't super useful independently (e.g. if you enable in the outliner but not in the inspector, then your changes won't actually trigger to be overrides, and if you only enable in inspector but not outliner, then you won't be able to even select entities in the outliner that overrides would apply to).

[alexmontAmazon]

It might be worth combining these into one section, because they aren't super useful independently (e.g. if you enable in the outliner but not in the inspector, then your changes won't actually trigger to be overrides, and if you only enable in inspector but not outliner, then you won't be able to even select entities in the outliner that overrides would apply to).

That's a good point, but this is at least a step forward. I'm going to merge this and then see about more drastic doc changes...