Use NPM provided version of SortableJS

What does this MR do?

• Removes vendor/assets/javascripts/Sortable.js in favour of NPM provided sortablejs from same author.
• Updates source files to reflect latest path of the package.

Why was this MR needed?

SortableJS in our vendor directory is 3 years old, so it only makes sense to move to npm package of it to ensure that we're on latest version and are taking Webpack's advantage.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests updated for this feature/bug
• Conform by the code review guidelines
  • [ ] Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • [ ] Has been reviewed by a Backend maintainer
  • [ ] Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• [ ] Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #47046 (closed)