R1:e875c81f6d2a

Remove blameRevision and revertPlan from the DifferentialRevision schema

Summary:
These fields use auxiliary storage now. Migrate the data and get rid of the
columns in the main table.

- This might take a little while to run, although there are <500k rows so
probably not too long.
- Maybe grab a backup of the table first, if I screwed something up this will
delete the data in these fields.

Test Plan:
- Ran migration locally.
- Browsed Differential.
- Grepped for "revertPlan" and…