Documentation out of date - userPayload depreciated field

[jackmead515]

Describe the bug
The documentation and examples clearly indicates that an EventSource of type "calendar" can define a userPayload as additional data to send in the event. The userPayload is a depreciated field and replaced with metadata

https://github.com/argoproj/argo-events/blob/v1.7.1/examples/event-sources/calendar.yaml#L32
https://argoproj.github.io/argo-events/eventsources/setup/calendar/

Environment (please complete the following information):

• Argo Events: [e.g. v1.7.1]

Additional context
Just need to update documentation and the examples with the new metadata argument.

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[whynowy]

Thanks, will fix it.