Remove unnecessary date picker related code change

[xinyis991105]

Description

This PR removes unnecessary date picker related code change.

Motivation and Context

#1376

How Has This Been Tested?

rails s and visit localhost:3000
Choose a course of your choice and click the upper right Manage Course. Click Course Settings to edit it.
If you scroll down to start and end date now, they should display appropriate date information. Date picker also works as expected, as below.

The previous error was likely due to the fact that moment.js doesn't recognize the flatpickr date formats.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation, which is located at Autolab Docs
• I have updated the documentation accordingly, included in this PR

Other issues / help required

If unsure, feel free to submit first and we'll help you along.

[fanpu]

Checked that scheduler, assessment, course datepickers all work

[magsol]

How would I merge this into a running Autolab instance? Would I be able to just jump into the running container and delete those 6 lines from the javascript file?

[xinyis991105]

Hi Shannon! Please reference our docs for update. If this is not a super urgent fix, we still suggest merging in the latest update, rebuilding the image, and running the new image. Let me know of any other questions.

[magsol]

Perfect, worked like a charm. Thank you so much!