Revert of [Sync] Enable UserEvents by default.

components/sync/driver/sync_driver_switches.cc

Index: components/sync/driver/sync_driver_switches.cc
diff --git a/components/sync/driver/sync_driver_switches.cc b/components/sync/driver/sync_driver_switches.cc
index c93cb0a36e685fb2456fff7aef634ef1c2186e00..1b346e21c5b4ab1228035273a574b1c530a0ea83 100644
--- a/components/sync/driver/sync_driver_switches.cc
+++ b/components/sync/driver/sync_driver_switches.cc
@@ -36,10 +36,9 @@
 const base::Feature kSyncClearDataOnPassphraseEncryption{
     "ClearSyncDataOnPassphraseEncryption", base::FEATURE_DISABLED_BY_DEFAULT};
 
-// Gates registration and construction of user events machinery. Enabled by
-// default as each use case should have their own gating feature as well.
+// Gates registration and construction of user events machinery.
 const base::Feature kSyncUserEvents{"SyncUserEvents",
-                                    base::FEATURE_ENABLED_BY_DEFAULT};
+                                    base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Gates registration for user language detection events.
 const base::Feature kSyncUserLanguageDetectionEvents{