wireshark: drop gmodule.h include to avoid glib warnings

wireshark: drop gmodule.h include to avoid glib warnings

The wireshark address.h header uses 'g_memdup2' but this triggers
warnings under clang due to the max version cap:

    In file included from ../tools/wireshark/src/plugin.c:27:
    In file included from /usr/include/wireshark/epan/proto.h:30:
    In file included from /usr/include/wireshark/epan/packet_info.h:15:
    /usr/include/wireshark/epan/address.h:107:18: error: 'g_memdup2' is deprecated: Not available before 2.68 [-Werror,-Wdeprecated-declarations]
      107 |     addr->priv = g_memdup2(&val, sizeof(val));
          |                  ^
    /usr/include/glib-2.0/glib/gstrfuncs.h:341:1: note: 'g_memdup2' has been explicitly marked deprecated here
      341 | GLIB_AVAILABLE_IN_2_68
          | ^
    /usr/include/glib-2.0/glib/glib-visibility.h:771:32: note: expanded from macro 'GLIB_AVAILABLE_IN_2_68'
      771 | #define GLIB_AVAILABLE_IN_2_68 GLIB_UNAVAILABLE (2, 68)
          |                                ^
    /usr/include/glib-2.0/glib/glib-visibility.h:32:35: note: expanded from macro 'GLIB_UNAVAILABLE'
       32 | #define GLIB_UNAVAILABLE(maj,min) G_UNAVAILABLE(maj,min) _GLIB_EXTERN
          |                                   ^
    /usr/include/glib-2.0/glib/gmacros.h:1285:47: note: expanded from macro 'G_UNAVAILABLE'
     1285 | #define G_UNAVAILABLE(maj,min) __attribute__((deprecated("Not available before " #maj "." #min)))
          |                                               ^
    1 error generated.

It is unclear why clang warns, but gcc does not. Our plugin doesn't
actually use the inline helper in address.h that references g_memdup2,
but we get the warning regardless.

Interestingly removing the 'gmodule.h' include avoids the warning. Since
there is nothing in plugin.c that appears to need gmodule.h, removing it
should be safe & done regardless.

Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>