[Bug] API Gateway v2 cookies response should be array

According to API Gateway v2 payload 2.0 docs (https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html) the 'cookies' should be array.
And below code is current handling logic for it.

https://github.com/vendia/serverless-express/blob/671f914429e9708bfb1ee6ba76b5947a917592df/src/event-sources/aws/api-gateway-v2.js#L65-L67

However, with the latest express (v4.17.1).
When user set cookie using `res.cookie(name, value)`, it set 'set-cookie' header as string at first time.
and convert it as array when using `res.cookie(name, value)` more than once.

So, we should insert Array check logic, and convert it to array when it is not.

Plus,
If we didn't delete 'set-cookie' header in response, API gateway send 'set-cookie' header twice.
So, for gateway v2 and payload 2.0 we should delete 'set-cookie' header field.

Beginne in src/event-sources/aws/api-gateway-v2.js bei der verknüpften Verarbeitungslogik und vergleiche das Antwortverhalten, wenn Express ein Cookie gegenüber mehreren Cookies setzt. Als abgeschlossen gilt, dass API Gateway v2 Cookies als Array empfängt und der ursprüngliche set-cookie-Header entfernt wird, damit er nicht zweimal gesendet wird.

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