Revert "Make FlexeLint a little bit happier"

The fact that a boolean argument is present does not imply
that it's true.

This reverts commit 57cd74cf.

I promise to look after this once I got my Flexelint config back,
which, unfortunately, I lost during a reinstall. Yes, I do have
a backup, but cannot access it easily at the moment.

lib/libvmod_debug/vmod_debug_obj.c

@@ -183,9 +183,6 @@ xyzzy_obj_opt__init(VRT_CTX,
 	if (args->valid_s)
 		AN(args->s);
 
-	if (args->valid_b)
-		AN(args->b);
-
 	AN(op);
 	AZ(*op);
 	ALLOC_OBJ(o, VMOD_DEBUG_OBJ_OPT_MAGIC);