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/parcelable_update_engine_status.h b/parcelable_update_engine_status.h
index 2050622..82006e4 100644
--- a/parcelable_update_engine_status.h
+++ b/parcelable_update_engine_status.h
@@ -39,7 +39,7 @@
 
   // This list is kept in the Parcelable serialization order.
 
-  // When the update_engine last checked for updates (ms since Epoch)
+  // When the update_engine last checked for updates (seconds since unix Epoch)
   int64_t last_checked_time_;
   // The current status/operation of the update_engine.
   android::String16 current_operation_;