address follow-ups from https://github.com/authzed/spicedb/pull/2782

[miparnisari]

• We should enable this:

spicedb/magefiles/test.go

Lines 257 to 266 in cbdf06c

	// Pgbouncer Run consistency tests for postgres with pgbouncer
	// FIXME actually implement this
	func (Testcons) Pgbouncer() error {
	println("postgres+pgbouncer consistency tests are not implemented")
	return nil
	}
	func (Testcons) PgbouncerVer(version string) error {
	println("postgres+pgbouncer consistency tests are not implemented")
	return nil

• We should update https://github.com/authzed/spicedb/blob/ef1a01bda3985d312d3b63fd83c20d01a1cb40d5/internal/datastore/postgres/README.md to mention pgbouncer and the pg_hint_plan extension
• We should turn on pg_hint_plan extension for the tests
• TestCheckPermissionOnTesterNoFlakes should be a unit test that doesn't need docker
• We should have autovacuum=off in all the postgres container tests