[BatchUpload] Fix SyncDisabled: true to return no local passwords

When sync service was unavailable, the JS callback mistakenly returned
"false" instead of "0" changing the underlying type of count in the Ui
from int to bool and causing a crash when trying to retrieve the plural
string using the count (interpreted as a bool).

Bug: 381063516, b:381047026
Change-Id: I81a63540cc4479af31480ff23a0f145b0228bb39
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6049959
Commit-Queue: Ryan Sultanem <rsult@google.com>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1388234}