Rename pending_assignment to pending_reassignment

What does this MR do and why?

Fixes #468506 (closed)

@rodrigo.tomonari:

Sometimes, we use the term 'assign' and, in other cases, the term 'reassign.' I wonder if we should be more consistent about this 🤔

This had already been renamed everywhere except for pending_assignment. This MR updates that state name.

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