bash_completion error for -h

Hi.
After updating aurget and spawning a new shell I got the following error:

```
bash: /etc/bash_completion.d/aurget: line 35: syntax error near unexpected token `return'
bash: /etc/bash_completion.d/aurget: line 35: `    -h|--@(help|ignore) return 0 ;;'
```

This patch should fix it.