Remove read_environment check for deployments

What does this MR do?

Fixes #219146 (closed)

For a public dashboard, the deployments endpoint was returning a 404 because an anonymous user doesn't have the :read_environment ability. This was removed in !32422 (merged)

Since the deployments controller only displays deployment info and is protected via the :read_deployment ability, I think we should be okay remove the :read_environment ability as in this MR.

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