Updates JavaScript for linting

[nateconley]

Description of the Change

• Updates jQuery Datepicker to use core version (this was previously completely broken.
  • Removes translated versions
• Fixes linting errors in JavaScript files

Closes #12

How to test the Change

• Ensure Datepicker works on frontend for Birthday field
• Ensure translated Datepicker works as expected
• Hide CSS table in admin works

Changelog Entry

Fixed - Datepicker display on frontend

Credits

@nateconley

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[nateconley]

@dkotter I have this PR targeted at the base linting branch. One open question for you: scrollTo is currently broken, seemingly due to it relying on an older version of jQuery that expectes $.browser. Should we update scrollTo as part of this implementation?

[dkotter]

One open question for you: scrollTo is currently broken, seemingly due to it relying on an older version of jQuery that expects $.browser. Should we update scrollTo as part of this implementation?

I'm not sure how that library is used here but I'd say let's address that as part of either #1 or #2. Depending on how that is used, we can replace with something else or maybe get rid of it all together