WebUI[MD-refresh]: replace paper-input with cr-input in cert-manager elements.

Bug: 832177
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Iac35742ffba55c0645a67f6a84813643076bd0e7
Reviewed-on: https://chromium-review.googlesource.com/1090003
Commit-Queue: Scott Chen <scottchen@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565760}