apt: ignore clippy lint about using a slice reference instead of &Vec

while the function would be more useful as pointed out by the clippy
lint, it i currently `pub` and users of the function would need to
adapt to the change here. so ignore the lint for now.

[1]: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_arg

Signed-off-by: Shannon Sterz <s.sterz@proxmox.com>

proxmox-apt/src/cache.rs

@@ -291,6 +291,7 @@ where
     None
 }
 
+#[allow(clippy::ptr_arg)]
 pub fn sort_package_list(packages: &mut Vec<APTUpdateInfo>) {
     let cache = apt_pkg_native::Cache::get_singleton();
     packages.sort_by(|left, right| {