Added pusher_type to create_properties and delete_properties webhooks

[vivekshotti]

Why:

Closes [#3192 ]

What's being changed:

So apparently The docs for DeleteEvent mention two fields, ref, and ref_type. However, there is a third field that appears in API calls, pusher_type. It seems pusher_type should also appear in the docs.

@skedwards88 later also pointed out that pusher_type is in the payload for DeleteEvent and also for CreateEvent, with values that can be user or a deploy key.

I've added the same in the reusable webhooks of create_properties and delete_properties.
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