Remove an unused member variable from VersionInfoUpdater

BootTimesLoader is no longer used since crrev.com/217006

BUG=443524
TEST=compiles

Review URL: https://codereview.chromium.org/811633010

Cr-Commit-Position: refs/heads/master@{#309192}

chrome/browser/chromeos/login/version_info_updater.h

@@ -65,9 +65,6 @@ class VersionInfoUpdater : public policy::CloudPolicyStore::Observer {
   // Callback from chromeos::VersionLoader giving the version.
   void OnVersion(const std::string& version);
 
-  // Handles asynchronously loading the boot times.
-  BootTimesLoader boot_times_loader_;
-
   // Information pieces for version label.
   std::string version_text_;
   std::string serial_number_text_;