Fix delete customgroup using API4 so it removes data table

[mattwire]

Overview

When using API3 CustomGroup.delete the associated data table is also deleted via a special function deleteGroup() But with API4 it is not because it's using the generic delete handling. This PR extends that so that the associated data table is deleted when called via API4.

Before

Custom group data table not deleted on API4 CustomGroup.delete

After

Custom group data table deleted on API4 CustomGroup.delete

Technical Details

Comments

@colemanw Does this make sense?

[civibot]

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[mattwire]

Thanks @colemanw I agree with your suggestion and have updated.

[colemanw]

I added a failing test and pushed it to this PR, so now if tests pass, we're good.