fix: delete-deployments behaviour

[erikburt]

This fixes some behavioural discrepancies I noticed with usages of the original action.

Changes

1. Make ref optional, as no ref is used here: https://github.com/smartcontractkit/chainlink/blob/develop/.github/workflows/delete-deployments.yml
2. Make environment required, as it's already used everywhere, and blanket deleting all deployments is probably a bad idea
3. Don't fallback to env values for a couple inputs, we can control the usages now, so we should call it properly

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DX-2999