--[Habitat3.0] Removal of out-of-date/deprecated flags for IBL

[jturner65]

Motivation and Context

IBL is now enabled and balanced against direct lighting in the PBR shader by settings in xxx.pbr_config.json files and programmatically via PbrShaderAttributes configurations.

These flags have been ignored since the IBL rework was merged here but this PR removes them.

NOTE : This is a breaking change, in that any code that is setting the flag will now break. Any code doing this can be removed without issue, since whatever the flag is set to has been ignored since the PBR/IBL rework.

How Has This Been Tested

All existing c++ and python tests pass.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[0mdc]

LGTM!

[aclegg3]

LGTM, thanks. Note this is breaking change since the flag is removed. Any code setting the flag elsewhere may error now.