Removing deprecated Database3.load() param

[john-science]

What is the change?

Removed unused updateGlobalAssemNum param from Database3.load().

Why is the change being made?

This parameter has been unused (and explicitly deprecated) in ARMI for over a year now. And I recently succeeded in removing all downstream references to it in other projects.

It's finally time to remove this thing.

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify that the new/changed code works.

• The code style follows good practices.
• The commit message(s) follow good practices.

• The release notes (location doc/release/0.X.rst) are up-to-date with any important changes.
• The documentation is still up-to-date in the doc folder.
• The dependencies are still up-to-date in pyproject.toml.

[john-science]

I ran downstream tests and they passed, so I'm merging.