Fix wording to comply with respectful-code

https://source.android.com/setup/contribute/respectful-code

Test: Run unit tests
Change-Id: Ia6647c9cf3224b962286151932118093b9ad979a
diff --git a/omaha_request_action.cc b/omaha_request_action.cc
index 3a0b91c..e37ebab 100644
--- a/omaha_request_action.cc
+++ b/omaha_request_action.cc
@@ -351,7 +351,7 @@
   // If we have the value stored on disk, just return it.
   int64_t stored_value;
   if (prefs->GetInt64(kPrefsInstallDateDays, &stored_value)) {
-    // Convert and sanity-check.
+    // Convert and validity-check.
     int install_date_days = static_cast<int>(stored_value);
     if (install_date_days >= 0)
       return install_date_days;