[`airflow`]: rename `AutoImport` as `Rename` (internal) (#20563)
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## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
Since we are trying to import both `AutoImport` and `SourceModuleMoved`,
the previous naming was not as descriptive. Renaming it to `Rename`
better reflects the intention.
## Test Plan
<!-- How was it tested? -->
no functionality change
