docs(expansion/table): tip use table option getRowId if data may change

[bobo96run]

Fix https://github.com/TanStack/table/issues/2028

Add a tip in https://tanstack.com/table/v8/docs/api/features/expanding to mention using the table option getRowId to avoid expansion glitch when table data changes.

Also mentioned in https://tanstack.com/table/v8/docs/api/core/table#getrowid that the option helps expansion.