Make aapt2 terminology more inclusive

Update language to comply with Android's inclusive language guidance

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

Bug: 162364131
Bug: 162536543
Test: aapt2_tests
Change-Id: I4eef925d6319b40a395fc8d59a3f2912a02ca03b
diff --git a/tools/aapt2/ResourceUtils.cpp b/tools/aapt2/ResourceUtils.cpp
index 469128b..7dfc983 100644
--- a/tools/aapt2/ResourceUtils.cpp
+++ b/tools/aapt2/ResourceUtils.cpp
@@ -740,7 +740,7 @@
   if (type == ResourceType::kId) {
     if (res_value.dataType != android::Res_value::TYPE_REFERENCE &&
         res_value.dataType != android::Res_value::TYPE_DYNAMIC_REFERENCE) {
-      // plain "id" resources are actually encoded as dummy values (aapt1 uses an empty string,
+      // plain "id" resources are actually encoded as unused values (aapt1 uses an empty string,
       // while aapt2 uses a false boolean).
       return util::make_unique<Id>();
     }