[extensions] Remove ExtensionService::TerminateExtension

Call ExtensionRegistrar::TerminateExtension instead of
ExtensionService::TerminateExtension

Bug: 410092899
Change-Id: I2ff7422165023bcee0f288b0a4889c6af8be2ac2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6454300
Reviewed-by: Owen Min <zmin@chromium.org>
Reviewed-by: Jan Keitel <jkeitel@google.com>
Reviewed-by: Jenny Zhang <jennyz@chromium.org>
Commit-Queue: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: David Bertoni <dbertoni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1447577}