Send `ip` parameter to Stripe instead of `browser_ip`

When you made the change in https://github.com/Shopify/active_merchant/commit/930175f5d9e3748b0bf883a2614ca7ec5518d0af it caused the issue where Stripe's API responded with the following error message:

```
Received unknown parameter: browser_ip
```

Stripe API expects a parameter `ip` and not `browser_ip`. If you send a parameter Stripe doesn't expect, the call fails.

Attached is code that'll take the option `browser_ip` but then assign it to the `ip` parameter that'll be sent to the Stripe API.