algorithms: Fix for_each_index build error caused by missing invoke include

Author: arpittkhandelwal

libs/core/algorithms/include/hpx/parallel/algorithms/for_each_index.hpp

@@ -73,6 +73,7 @@ namespace hpx { namespace experimental {
 #else
 
 #include <hpx/config.hpp>
+#include <hpx/functional/invoke.hpp>
 #include <hpx/modules/concepts.hpp>
 #include <hpx/modules/execution.hpp>
 #include <hpx/modules/executors.hpp>