Script to delete the extra EASDevices for an account.

Summary:
Certain EASAccounts have more than one pair of EASDevices due to reauth. I plan to roll out a
real fix for the issue shortly (updated: revision D727).
To back-fix, prune the superseded EASDevice pairs for these accounts.

Test Plan:
Tested on a prod replica.

Planning to run online in prod -
There are 6 affected accounts, the script takes ~5minutes to run (due to the EASUid deletes).

Reviewers: emfree

Reviewed By: emfree

Differential Revision: https://review.inboxapp.com/D726