WebUI: Delete iron-location Polymer2 element and remove from build.

The element is no longer used anywhere.

Bug: 1173575
Change-Id: I688b4b22bbcc3080802f8febe30e76fbf9636910
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2727335


Commit-Queue: John Lee <johntlee@chromium.org>
Auto-Submit: dpapad <dpapad@chromium.org>
Reviewed-by: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#859597}