Move landing page new notebook to the bottom

Since these event handlers are removed and not used, they should also be removed in the `$destroy` handler, (i.e. line [417](https://github.com/twosigma/beaker-notebook/blob/9aafc8f01b3d9b90631e2ce2e5115efca57917bc/core/src/main/web/app/mainapp/components/notebook/codecell-directive.js#L417), [418](https://github.com/twosigma/beaker-notebook/blob/9aafc8f01b3d9b90631e2ce2e5115efca57917bc/core/src/main/web/app/mainapp/components/notebook/codecell-directive.js#L418))