chore(zygisk): drop redundant allow(dead_code) on is_vpn_iface_cstr

The function is called from hooks.rs (hooked_getifaddrs and
walk_getifaddrs_vpn). It's been used since the helper was added —
the allow attribute is leftover from before its callers landed.
clippy --release and cargo test both clean without it.

zygisk/src/filter.rs

@@ -23,7 +23,6 @@ pub fn is_vpn_iface_bytes(name: &[u8]) -> bool {
 }
 
 /// Convenience wrapper: takes a `CStr` and dispatches to `is_vpn_iface_bytes`.
-#[allow(dead_code)]
 pub fn is_vpn_iface_cstr(name: &CStr) -> bool {
     is_vpn_iface_bytes(name.to_bytes())
 }