Don't use HAVE_CONFIG_H in sample code in the documentation.

We require config.h and don't define HAVE_CONFIG_H - it should *always*
be included.

doc/plugins.example/hello.c

@@ -7,9 +7,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
-#ifdef HAVE_CONFIG_H
 #include "config.h"
-#endif
+
 #define WS_BUILD_DLL
 #include <wireshark.h>
 #include <epan/packet.h>

docbook/wsdg_src/WSDG_chapter_asn2wrs.adoc

@@ -876,9 +876,7 @@ Replace all PROTOCOL/protocol references with the name of your protocol.
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
-#ifdef HAVE_CONFIG_H
-# include "config.h"
-#endif
+#include "config.h"
 
 #include <glib.h>
 #include <epan/packet.h>