nixos/test-driver: add 10ms delay to send_key

attempt to fix https://github.com/NixOS/nixpkgs/issues/147294

nixos/lib/test-driver/test-driver.py

@@ -916,6 +916,7 @@ class Machine:
     def send_key(self, key: str) -> None:
         key = CHAR_TO_KEY.get(key, key)
         self.send_monitor_command("sendkey {}".format(key))
+        time.sleep(0.01)
 
     def start(self) -> None:
         if self.booted: