fix user upcoming events for more than 20 assignments
fix user upcoming events for more than 20 assignments

test plan:
* when a user has more than 20 assignments with upcoming due dates,
the earliest events should always be shown first

closes #CNVS-29897 frd

Change-Id: Ic1a7c611c98bae5c2d31ac696e0f45560e46adb9
Reviewed-on: https://gerrit.instructure.com/91077
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
QA-Review: David Tan <6283e310a2278fc51bdc4fb5974f70dd9c3366b9@instructure.com>
Product-Review: James Williams  <3a5f4ed991dbfa5c9ef76ad729d240ca12f62180@instructure.com>

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