Download script not working

The download script is broken. The generated download URL is wrong.

```bash
# Command
wget -qO- cli.runpod.net | sudo bash

# Download URL
https://github.com/runpod/runpodctl/releases/download/v1.14.15/runpodctl_1.14.15_linux_amd64.tar.gz

# Correct
https://github.com/runpod/runpodctl/releases/download/v1.14.15/runpodctl-linux-amd64.tar.gz
```