Fix Python API docs build error

There is probably a better solution that's possible, but the few other
things I tried didn't work, and the build error should be resolved for
the buildbots. This is similar to the "breaks" in the namespace for
functions declared in `ED_node.h`.

source/blender/editors/space_node/space_node.cc

@@ -816,8 +816,14 @@ static void node_region_listener(const wmRegionListenerParams *params)
   }
 }
 
+}  // namespace blender::ed::space_node
+
+/* Outside of blender namespace to avoid Python documentation build error with `ctypes`. */
 const char *node_context_dir[] = {
     "selected_nodes", "active_node", "light", "material", "world", nullptr};
+
+namespace blender::ed::space_node {
+
 static int /*eContextResult*/ node_context(const bContext *C,
                                            const char *member,
                                            bContextDataResult *result)