Remove obsolete Installer.* metrics.

These metrics were replaced by the UpdateEngine.* metrics.

Bug: chromium:355745
Test: FEATURES=test emerge-link update_engine

Change-Id: I80d0db44681c428898500dd9099918e98ae40b28
diff --git a/error_code.h b/error_code.h
index 417e585..fdef895 100644
--- a/error_code.h
+++ b/error_code.h
@@ -90,7 +90,7 @@
   // particular value for this enum so that it's just one more than the last
   // one above and thus always represents the correct count of UMA metrics
   // buckets, even when new enums are added above this line in future. See
-  // utils::SendErrorCodeToUma on how this enum is used.
+  // metrics::ReportUpdateAttemptMetrics() on how this enum is used.
   kUmaReportedMax,
 
   // use the 2xxx range to encode HTTP errors. These errors are available in