Update PasswordSyncState enum to match password_manager_metrics_util.h

Recent patch has added new entries to the PasswordSyncState enum
in password_manager_metrics_util.h and didn't update the corresponding
enum in histograms/enums.xml.

https://chromium-review.googlesource.com/c/chromium/src/+/1552822

This CL updates histograms/enums.xml to match
password_manager_metrics_util.h

Bug: 949493
Change-Id: Ia432689604385b8e9d482ad4a8dea4e69b3d9569
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1581341Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653524}

tools/metrics/histograms/enums.xml

@@ -44150,6 +44150,9 @@ Called by update_net_trust_anchors.py.-->
   <int value="3" label="Server failed"/>
   <int value="4" label="Cleanup failed"/>
   <int value="5" label="Decryption failed"/>
+  <int value="6" label="Add failed"/>
+  <int value="7" label="Update failed"/>
+  <int value="8" label="Metadata persistence failed"/>
 </enum>
 
 <enum name="PaymentRequestAbortReason">