dftest: Don't use quotes to output filter

Using quotes is confusing because they are difficult to distinguish
from the actual filter expression itself. Quotes are unnecessary
anyway because whitespace is not significant (except inside brackets).

dftest.c

@@ -130,7 +130,7 @@ main(int argc, char **argv)
 	/* Get filter text */
 	text = get_args_as_string(argc, argv, 1);
 
-	printf("Filter: \"%s\"\n", text);
+	printf("Filter: %s\n", text);
 
 	/* Compile it */
 	if (!dfilter_compile(text, &df, &err_msg)) {