[ios] Bump CHECK in PrefBackedBoolean from M140 to M145

Since it appears that there are many pre-existing codepath
leading to this CHECK failing, mark it as non-fatal until
M-145 to give more time to fix those issues.

Change-Id: If9ab19e4cec2e960c22990ba22713db707e5a220
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6667843
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1478900}