Fix postgres schema after dropping old tables

[DMRobertson]

This resolves a conflict between
#16658 and #16652
and should unsad CI.

[Half-Shot]

Aha, this is why #16729 is failing. Thanks!

[DMRobertson]

The migrations I deleted should correspond exactly to the tables in this delta:

synapse/synapse/storage/schema/main/delta/83/01_drop_old_tables.sql

Lines 16 to 24 in 579c6be

	-- Drop the old event transaction ID table, the event_txn_id_device_id table
	-- should be used instead.
	DROP TABLE IF EXISTS event_txn_id;
	-- Drop tables related to MSC2716 since the implementation is being removed
	DROP TABLE IF EXISTS insertion_events;
	DROP TABLE IF EXISTS insertion_event_edges;
	DROP TABLE IF EXISTS insertion_event_extremities;
	DROP TABLE IF EXISTS batch_events;