Update scope:for_self_hosted_dap to use new addon name

What does this MR do and why?

Previously, MR Add a new SKU scope for self hosted dap (!214790 - merged) created an the dummy scope: for_self_hosted_dap.

As we renamed the AddOn name from duo_self_hosted to self_hosted_dap (done by MR Rename `duo_self_hosted` AddOn to `self_hosted_... (!215965 - merged)), now we should update scope: for_self_hosted_dap to find the real addon self_hosted_dap.

This MR basically:

• revert the dummy scope introduced by MR Rename `duo_self_hosted` AddOn to `self_hosted_... (!215965 - merged)
• rename scope: for_duo_self_hosted to scope: for_self_hosted_dap

With this MR, the scope for_self_hosted_dap returns real self_hosted_dap AddOns.

BTW: the scope is usually used combined with other scopes, such as to find the AddOn GitlabSubscriptions::AddOnPurchase.for_self_managed.for_self_hosted_dap.first, or to find the active AddOn GitlabSubscriptions::AddOnPurchase.for_self_managed.for_self_hosted_dap.active.first (exists? / any? / etc)

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Related to #583583