Add tooltip to RestrictedRadioButtons on file permission editor
Add tooltip to RestrictedRadioButtons on file permission editor

Refs LA-626
flag=none

Test plan:
 - Go to files for a course
 - Click "Manage access"
 - Click "Schedule student availability"
 - When hovering over date box, tooltip should appear that shows
   the correct input format

Change-Id: I284972500b61aa0a305693085d5a7ae267d721ca
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/239294
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>
QA-Review: Robin Kuss <0b206b54367b2de0334896ea45826f0e3194bd35@instructure.com>
Product-Review: Jackson Howe <318c10a818c1b1f2ec50cdcb1827b2c6c5ebd7dc@instructure.com>

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