SceneCacheData.cpp: expansionRule token removed from header in USD 22.03

[lucienfostier]

• SceneCacheData: Fix compatibility with USD 22.03
  • USD 22.03 removed expansionRule token from its header. Hardcoding the property name to continue creating Collection with that property for each set from SceneCache.

Related Issues

• List any Issues this PR addresses or solves

Dependencies

• List any other unmerged PRs that this PR depends on

Breaking Changes

• List any breaking API/ABI changes

Checklist

• I have read the contribution guidelines.
• I have updated the documentation, if applicable.
• I have tested my change(s) in the test suite, and added new test cases where necessary.
• My code follows the Cortex project's prevailing coding style and conventions.

[johnhaddon]

Just trying to get my head around this. The USD changelog doesn't seem to say that expansion rule is deprecated, but rather that...

"expansionRule" attribute for UsdCollectionAPI is now optional; collections are created simply by calling UsdCollectionAPI::ApplyCollection.

So it sounds like it is OK to omit it as we're doing now, but I don't understand why we need to omit it - could you educate me?