init: replace Result<Success> with Result<void>

Now that Result<T> is actually expected<T, ...>, and the expected
proposal states expected<void, ...> as the way to indicate an expected
object that returns either successfully with no object or an error,
let's move init's Result<Success> to the preferred Result<void>.

Bug: 132145659
Test: boot, init unit tests
Change-Id: Ib2f98396d8e6e274f95a496fcdfd8341f77585ee
diff --git a/init/builtins.h b/init/builtins.h
index 814b2d5..5db0d1c 100644
--- a/init/builtins.h
+++ b/init/builtins.h
@@ -29,7 +29,7 @@
 namespace android {
 namespace init {
 
-using BuiltinFunction = std::function<Result<Success>(const BuiltinArguments&)>;
+using BuiltinFunction = std::function<Result<void>(const BuiltinArguments&)>;
 
 using KeywordFunctionMap = KeywordMap<std::pair<bool, BuiltinFunction>>;
 class BuiltinFunctionMap : public KeywordFunctionMap {