Call the `request` method rather than `post`
Call the `request` method rather than `post`

The return type of Configuration::getSessionClient is
"GuzzleHttp\ClientInterface", which doesn't define a 'post' method
— it's defined on the GuzzleHttp\Client concrete class instead

If we're using the interface here (which makes sense!) then we should
only rely on the methods that exist on the interface

bugsnag/bugsnag-php,bugsnag/bugsnag-php,bugsnag/bugsnag-php