Upgrade react-modal
Upgrade react-modal

Test plan:
* look at https://github.com/reactjs/react-modal/blob/master/CHANGELOG.md#v3111---fri-25-oct-2019-210209-utc
* and make sure there is nothing there that would affect us
* make sure places where we use react-modal still work

Change-Id: I70fe7676d2b62782ea613975591e33b6c646f1de
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/218795
Tested-by: Jenkins
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Steven Burnett <a0b450117c5d20a22d5c4d52bb8ae13adee003d8@instructure.com>
QA-Review: Steven Burnett <a0b450117c5d20a22d5c4d52bb8ae13adee003d8@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

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