Comment out unused ModelTypeForHistograms entries

Since this is a histogram enum, the entries are commented out but left
around, for historical purposes and to reduce the chances of reuse.

Bug: 1012648, 1007293
Change-Id: Ic931270a50908e4977e2ca2fd7f6851fab3dcfed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1852253
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Jan Krcal <jkrcal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705511}

components/sync/base/model_type.h

@@ -192,24 +192,24 @@ enum class ModelTypeForHistograms {
   kApps = 12,
   kAppSettings = 13,
   kExtensionSettings = 14,
-  kDeprecatedAppNotifications = 15,
+  // kDeprecatedAppNotifications = 15,
   kHistoryDeleteDirectices = 16,
   kNigori = 17,
   kDeviceInfo = 18,
   kDeprecatedExperiments = 19,
-  kDeprecatedSyncedNotifications = 20,
+  // kDeprecatedSyncedNotifications = 20,
   kPriorityPreferences = 21,
   kDictionary = 22,
   kFaviconImages = 23,
   kFaviconTracking = 24,
   kProxyTabs = 25,
   kSupervisedUserSettings = 26,
-  kDeprecatedSupervisedUsers = 27,
-  kDeprecatedArticles = 28,
+  // kDeprecatedSupervisedUsers = 27,
+  // kDeprecatedArticles = 28,
   kAppList = 29,
-  kDeprecatedSupervisedUserSharedSettings = 30,
-  kDeprecatedSyncedNotificationAppInfo = 31,
-  kDeprecatedWifiCredentials = 32,
+  // kDeprecatedSupervisedUserSharedSettings = 30,
+  // kDeprecatedSyncedNotificationAppInfo = 31,
+  // kDeprecatedWifiCredentials = 32,
   kSupervisedUserWhitelists = 33,
   kAutofillWalletData = 34,
   kAutofillWalletMetadata = 35,