Add environment explanation to Deployment SLO definition.

Why is this change being made?

The Deployment SLO definition on the Releases page is reporting two environments that are not fully correct and they don't represent the current way the metric is calculated.

This MR added more specifics around the environments and a reference to the overview process that can clarify what are these environments and where they are involved during the deployment process.

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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