fix: conditionally include endpoint_urls in deployment dictionary

[Haivilo]

What does this PR address?

Listing deployment does not have endpoint urls, only get deployment. We might want to ignore it to to avoid confusion, e.g., bentoml deployment list -o json should not have "endpoint_urls": null.

Another possibility is that we can also do it by deleting the key manually when -o json is used.

Fixes #(issue)

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