vhost_user_net: reevaluate #[allow] attributes

Convert the still-needed #[allow] to #[expect] so it warns if the
lint stops firing.

Part of #8326.

Signed-off-by: Tushar Khatri <hello@tusharkhatri.in>

vhost_user_net/src/lib.rs

@@ -119,7 +119,7 @@ pub struct VhostUserNetBackend {
 }
 
 impl VhostUserNetBackend {
-    #[allow(clippy::too_many_arguments)]
+    #[expect(clippy::too_many_arguments)]
     fn new(
         ip_addr: IpAddr,
         host_mac: MacAddr,