Revert of [Telemetry] Reenable unused-import lint check for telemetry. (patchset...

Revert of [Telemetry] Reenable unused-import lint check for telemetry. (patchset #1 id:40001 of https://codereview.chromium.org/1051323006/)

Reason for revert:
Failing telemetery_unittests on Linux Tests bot:

https://sheriff-o-matic.appspot.com/chromium/failure/telemetry_unittests%3A%3ALinux%20Tests

Original issue's description:
> [Telemetry] Reenable unused-import lint check for telemetry.
>
> Fix all the places that have unused-import in telemetry.
>
> BUG=475714
>
> Committed: https://crrev.com/dced4517e3fe208cd5d02ee361b43132afec870d
> Cr-Commit-Position: refs/heads/master@{#326298}

TBR=sullivan@chromium.org,dtu@chromium.org,nednguyen@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=475714

Review URL: https://codereview.chromium.org/1060063007

Cr-Commit-Position: refs/heads/master@{#326314}