🐛 Add missing #pragma once directives

Problem:
- Two headers are missing `#pragma once`.

Solution:
- Add it.

Author: bdeane-intel

include/flow/graphviz_builder.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 #include <flow/detail/walk.hpp>
 
 #include <stdx/tuple_algorithms.hpp>

include/log/catalog/builder.hpp

@@ -1,3 +1,5 @@
+#pragma once
+
 #include <log/catalog/mipi_builder.hpp>
 
 #include <stdx/compiler.hpp>