Correct variable name for last update check time

Align the name of the last update check time variable to the units
within it (seconds since epoch).

Bug: 70178109
Test: unit-tests
Change-Id: Ic06890f0e234528d80dc1bcd053e8b602c6f9309
(cherry picked from commit 4adf279cecb8b6c5f85d66e504b9c847b72e0e4c)
diff --git a/update_attempter.cc b/update_attempter.cc
index a6f9fa5..5c9c44a 100644
--- a/update_attempter.cc
+++ b/update_attempter.cc
@@ -1170,7 +1170,7 @@
 }
 
 bool UpdateAttempter::GetStatus(UpdateEngineStatus* out_status) {
-  out_status->last_checked_time_ms = last_checked_time_;
+  out_status->last_checked_time = last_checked_time_;
   out_status->status = status_;
   out_status->current_version = omaha_request_params_->app_version();
   out_status->current_system_version = omaha_request_params_->system_version();