The following changes need to be made:

• Migrations should succeed on both source and destination up/downgrade.
• Since there is no longer a writeConcern parameter mismatch on latest and last-stable, we should remove the test case testMigrateFromLastStableToLatest or just assert it succeeds
• FCV no longer blocks on a migration, so we should test the inverse.

Once this is complete, remove the migrations_with_mixed_fcv.js test blacklists.