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/subcontext_benchmark.cpp b/init/subcontext_benchmark.cpp
index 6307993..fdbbc41 100644
--- a/init/subcontext_benchmark.cpp
+++ b/init/subcontext_benchmark.cpp
@@ -53,7 +53,7 @@
 TestFunctionMap BuildTestFunctionMap() {
     TestFunctionMap test_function_map;
     test_function_map.Add("return_success", 0, 0, true,
-                          [](const BuiltinArguments& args) { return Success(); });
+                          [](const BuiltinArguments& args) { return Result<void>{}; });
 
     return test_function_map;
 }