boost: remove process/child.hpp

Boost 1.88 removes the process/child.hpp header.  We are not actually
using it, but do need the replace_all algorithm.  Adjust the include
to point to the needed header instead of one we get indirectly (and
which won't exist in the future).

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9e4d46179d7c55082aa18c74b11fd3b0aeb89120
diff --git a/src/entity_manager/overlay.cpp b/src/entity_manager/overlay.cpp
index 1a389fb..7d7de96 100644
--- a/src/entity_manager/overlay.cpp
+++ b/src/entity_manager/overlay.cpp
@@ -21,11 +21,11 @@
 #include "utils.hpp"
 
 #include <boost/algorithm/string/predicate.hpp>
+#include <boost/algorithm/string/replace.hpp>
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/steady_timer.hpp>
 #include <boost/container/flat_map.hpp>
 #include <boost/container/flat_set.hpp>
-#include <boost/process/child.hpp>
 #include <nlohmann/json.hpp>
 #include <phosphor-logging/lg2.hpp>