general: Replace RESULT_UNKNOWN with ResultUnknown

Transition to PascalCase for result names.

src/core/hle/service/aoc/aoc_u.cpp

@@ -190,7 +190,7 @@ void AOC_U::ListAddOnContent(Kernel::HLERequestContext& ctx) {
     if (out.size() < offset) {
         IPC::ResponseBuilder rb{ctx, 2};
         // TODO(DarkLordZach): Find the correct error code.
-        rb.Push(RESULT_UNKNOWN);
+        rb.Push(ResultUnknown);
         return;
     }