disas: Remove unused macro '_'

Eliminates a future compilation error when UI code includes the tracing
headers (indirectly pulling "disas/bfd.h" through "qom/cpu.h") and
GLib's i18n '_' macro.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/disas/i386.c b/disas/i386.c
index c0e717a..57145d0 100644
--- a/disas/i386.c
+++ b/disas/i386.c
@@ -3406,7 +3406,7 @@
   }
 };
 
-#define INTERNAL_DISASSEMBLER_ERROR _("<internal disassembler error>")
+#define INTERNAL_DISASSEMBLER_ERROR "<internal disassembler error>"
 
 static void
 ckprefix (void)