Add Deliverable label to Quad Planning approach

Why is this change being made?

As per the new Product development workflow, the Deliverable label is a required one in the Plan phase - https://about.gitlab.com/handbook/product-development-flow/#required-labels which indicates that the specified issue has been accepted into the current milestone. As we are generating the quad planning report on a weekly bases now for all groups with SETs, would it be more meaningful to only include issues with the Deliverable label. I will create another MR in triageops repo if we decide to go in that direction and also once every group starts to follow the new pd-flow religiously.

@gl-quality/managers Following Gitlab values and wanted to open up this conversation with an MR. Kindly provide feedback.

This MR should close #9130 (closed).

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