[NTP] Fix delete link on "enter" in the edit dialog

Pressing enter in the edit link dialog will no longer delete the link.
The current event handler was not being called.

Bug: 864357
Change-Id: Idbba0cf0a3f9f0afa7dbcf91b49ec45de5c9e144
Reviewed-on: https://chromium-review.googlesource.com/1169763
Commit-Queue: Kristi Park <kristipark@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582020}