Reland "Clean up old OWNERS in /importer"

This is a reland of commit e609aeba56ae7578e14c2e861f63ca1014cc854b
Reverted @ https://chromium-review.googlesource.com/c/chromium/src/+/6577869
because of removing //ipc/SECURITY_OWNERS entries

Original change's description:
> Clean up old OWNERS in /importer
>
> isherman left a few weeks ago and I'm not a good owner to remain here
> solo (I became an owner after touching this 12 years ago but mostly
> relied on isherman for anything meaty)
>
> As discussed with groby/robliao: Removing self in order to fall back to
> //chrome owners.
>
> Change-Id: I12b8bd6e4dc7f7344e52207a61e69e84bce48064
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6574900
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Auto-Submit: Gabriel Charette <gab@chromium.org>
> Reviewed-by: Erik Chen <erikchen@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1463832}

Change-Id: I51e7225f2c47fc2b367cfbcf14b81d5acbe1488c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6579143
Reviewed-by: Erik Chen <erikchen@chromium.org>
Auto-Submit: Gabriel Charette <gab@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1464091}