Makes quota labels read by screenreaders

Uses labelled-by to force screenreaders to read the labels,
this shouldn't be needed, but for some odd reason here it
was.

fixes CNVS-13909

Test Plan:
  - Using a screenreader (NVDA) go to the accounts settings
    page on the quotas tab
  - Navigate to the quota inputs
  - The screenreader should read the various labels so that
    you can tell which quota you are editing.

Change-Id: I8d5683e67808115027b18732c77c770b40998cc7
Reviewed-on: https://gerrit.instructure.com/40377
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Reviewed-by: Ryan Shaw <ryan@instructure.com>
QA-Review: Nathan Rogowski <nathan@instructure.com>
Product-Review: Cosme Salazar <cosme@instructure.com>