increase default column width for easier grade entry
increase default column width for easier grade entry

Fixes CNVS-36917

Test plan:
* Create an assignment out of 10 points possible
* Load new gradebook
* Make sure you can enter a grade and see the whole input

Change-Id: Ia6ff551f450d5a3fe7bdfb36541a69703afc2ad4
Reviewed-on: https://gerrit.instructure.com/112936
Tested-by: Jenkins
QA-Review: KC Naegle <9fbecd016338f9910821a8a5d5d0ae4fc9abfaa5@instructure.com>
Reviewed-by: Jeremy Neander <20252aad5efdc666f083d82ab63ed0f9f72a043e@instructure.com>
Product-Review: Keith T. Garner <a1a80143a840c140f31c3495ebbd9ec906e09fed@instructure.com>

djbender/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms