do not use 'first' for this migration
do not use 'first' for this migration

first was using "order by" to step through the
whole attachments table which can take 30s or so
per iteration of this inner loop. `take` applies the filter
first.

TEST PLAN:
 1) run migrations
 2) should not take forever on high-attachment shard

Change-Id: I450a0254195929a76bd5725e10ea56c02164437a
Reviewed-on: https://gerrit.instructure.com/79646
Reviewed-by: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
Tested-by: Jenkins
Product-Review: Ethan Vizitei <73eeb0b2f65d05a906adf3b21ee1f9f5a2aa3c1c@instructure.com>
QA-Review: Ethan Vizitei <73eeb0b2f65d05a906adf3b21ee1f9f5a2aa3c1c@instructure.com>

fronteerio/canvas-lms,SwinburneOnline/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,dgynn/canvas-lms,matematikk-mooc/canvas-lms,fronteerio/canvas-lms,fronteerio/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,venturehive/canvas-lms,fronteerio/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,sfu/canvas-lms,roxolan/canvas-lms,SwinburneOnline/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,grahamb/canvas-lms,matematikk-mooc/canvas-lms,HotChalk/canvas-lms,dgynn/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,HotChalk/canvas-lms,venturehive/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,roxolan/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,dgynn/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms