GNATCOLL.JSON.Utility: move unused WITH clause

This fixes a warning with recent GNAT toolchains, which now detect more
unused WITH clauses.

Change-Id: I38cbeecfff49a3b1107f42a2857966ecc75c5e32
TN: T811-027

Author: pmderodat

src/gnatcoll-json-utility.adb

@@ -1,7 +1,7 @@
 ------------------------------------------------------------------------------
 --                             G N A T C O L L                              --
 --                                                                          --
---                     Copyright (C) 2011-2018, AdaCore                     --
+--                     Copyright (C) 2011-2020, AdaCore                     --
 --                                                                          --
 -- This library is free software;  you can redistribute it and/or modify it --
 -- under terms of the  GNU General Public License  as published by the Free --
@@ -29,6 +29,8 @@ with Interfaces;                       use Interfaces;
 with GNAT.Encode_UTF8_String;
 with GNAT.Decode_UTF8_String;
 
+with GNATCOLL.Strings;
+
 package body GNATCOLL.JSON.Utility is
 
    use Ada.Strings.Unbounded;

src/gnatcoll-json-utility.ads

@@ -1,7 +1,7 @@
 ------------------------------------------------------------------------------
 --                             G N A T C O L L                              --
 --                                                                          --
---                     Copyright (C) 2011-2017, AdaCore                     --
+--                     Copyright (C) 2011-2020, AdaCore                     --
 --                                                                          --
 -- This library is free software;  you can redistribute it and/or modify it --
 -- under terms of the  GNU General Public License  as published by the Free --
@@ -21,8 +21,6 @@
 --                                                                          --
 ------------------------------------------------------------------------------
 
-with GNATCOLL.Strings;
-
 private package GNATCOLL.JSON.Utility is
 
    JsonMimeType           : constant String := "application/json";