Update language to comply with Android's inclusive language guidance

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

#inclusivefixit

Bug: 161896447
Change-Id: I62b6d5016433cd8b971326c771fb39ccb85827d1
Test: Build pass
diff --git a/omaha_request_params.cc b/omaha_request_params.cc
index d4b8d64..8a2e3dc 100644
--- a/omaha_request_params.cc
+++ b/omaha_request_params.cc
@@ -66,7 +66,7 @@
   image_props_ = LoadImageProperties(system_state_);
   mutable_image_props_ = LoadMutableImageProperties(system_state_);
 
-  // Sanity check the channel names.
+  // Validation check the channel names.
   if (!IsValidChannel(image_props_.current_channel))
     image_props_.current_channel = "stable-channel";
   if (!IsValidChannel(mutable_image_props_.target_channel))