Revert "Move to unordered_map"

This reverts commit 5610321.

Signed-off-by: Luca Della Vedova <lucadv@intrinsic.ai>

Author: luca-della-vedova

include/gz/physics/CompositeData.hh

@@ -19,9 +19,9 @@
 #define GZ_PHYSICS_COMPOSITEDATA_HH_
 
 #include <string>
+#include <map>
 #include <set>
 #include <typeindex>
-#include <unordered_map>
 
 #include <gz/utils/SuppressWarning.hh>
 
@@ -964,7 +964,7 @@ namespace gz
 
       // We make this typedef public so that helper functions can use it without
       // being friends of the class.
-      public: using MapOfData = std::unordered_map<std::type_index, DataEntry>;
+      public: using MapOfData = std::map<std::type_index, DataEntry>;
 
       GZ_UTILS_WARN_IGNORE__DLL_INTERFACE_MISSING
       /// \brief Map from the label of a data object type to its entry