WebUI: paper-input clean-ups.

This CL cleans up some remnant of paper-input, now that paper-input is
mostly removed.

Bug: 720276
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Id17298df731d1fbfc111fdb6db40202e1036dd4a
Reviewed-on: https://chromium-review.googlesource.com/1139086
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Scott Chen <scottchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575892}
6 files changed