Improve 4s-query man page

man/4s-query.1

@@ -17,7 +17,7 @@ kb-name
 .Op query
 .Bl -tag -width indent
 .It Fl f
-Set the format to output results it, options are "sparql", "text", and "testcase"
+Set the format to output results it, options are "sparql", "text", "json", and "testcase"
 .It Fl "O, \-\-opt-level"
 Set the optimisation level of the query engine, in the range 0-3.
 .It Fl "I, \-\-insert"