tdf#42949 Replace property_tre/json_parser.hpp with fw declaration header

Similarly to commit fb1b461208e7a2760fa1c018db08606a9b3e435d replace
new instances of boost/property_tree/json_parser.hpp with forward declaration
only header, as suggested by IWYU.

Change-Id: I9f1cc3e3b1fa0a98326d6f22823860fbde2f81a2
Reviewed-on: https://gerrit.libreoffice.org/85168
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
diff --git a/include/svx/xflftrit.hxx b/include/svx/xflftrit.hxx
index 935bf55..3865bd5 100644
--- a/include/svx/xflftrit.hxx
+++ b/include/svx/xflftrit.hxx
@@ -22,7 +22,7 @@

#include <svx/xflgrit.hxx>
#include <svx/svxdllapi.h>
#include <boost/property_tree/json_parser.hpp>
#include <boost/property_tree/ptree_fwd.hpp>