fix incorrect example in rtl_Instance docs

Change-Id: I1cb0c9bfca7ebcf8de96ef25554a41d52b9d7df5

include/rtl/instance.hxx

@@ -219,7 +219,7 @@ namespace {
       T * getInstance()
       {
           return rtl_Instance< T, InitInstance,
-                               ::osl::Mutex, ::osl::GetGlobalMutex,
+                               ::osl::MutexGuard, ::osl::GetGlobalMutex,
                                Data, InitData >::create(
               InitInstance(), ::osl::GetGlobalMutex(), InitData());
       }