Approve button for rollout should say 'rollout' not 'experiment'

[jaredlockhart]

I just noticed when launching a rollout that the approve button says 'Approve and Launch Experiment' even if it's marked as a rollout. In other cases we say 'End Rollout' rather than 'End Experiment', so we should make sure the buttons always correctly identify whether an experiment or rollout is being manipulated, otherwise this can cause confusion. There's no point in fixing this in the current UI but as we implement the new HTMX UI we should make sure to keep this consistent.

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