use new proxmox-async crate

Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>

examples/download-speed.rs

@@ -59,7 +59,7 @@ async fn run() -> Result<(), Error> {
 }
 
 fn main() {
-    if let Err(err) = pbs_runtime::main(run()) {
+    if let Err(err) = proxmox_async::runtime::main(run()) {
         eprintln!("ERROR: {}", err);
     }
     println!("DONE");