[SYNC] Clean up num_encryption_conflicts.

num_encryption_conflicts of StatusController only update in test. That
means it's always 0 in product. Remove it. Reflected updates counter is
removed from sync-internals and a corresponding proto field is not
filled in anymore.

Bug: 1315573
Change-Id: I7942b52035f5297232ea7256e0243fac54fc154c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3614387
Reviewed-by: Rushan Suleymanov <rushans@google.com>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: qian zhuoyu <zhuoyuqian@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#999482}