Clarify danger is not a valid type of IconButton or <Button hasIconOnly/>

[tay1orjones]

This has been a point of confusion for some time (#11484, #14295) and we have not clearly stated anywhere on the website or storybook (that I can find) that we do not support danger for the icon only button(s).

This includes both IconButton, and Button with hasIconOnly.

Pieces to fix

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1. Double check the types for IconButton do not allow danger
2. docs(button): specify danger is not supported for icon only buttons #14307
   role: dev 🤖 status: ready to merge 🎉 type: docs 📖 +3
   
3. Button: Update types to be a conditional proptype (or a union in TS) of if hasIconOnly, kind !== "danger" #17036
   component: button package: @carbon/react role: dev 🤖 +3
   
4. Button: add guidance for not having danger icon only buttons carbon-website#4176
   component: button role: design ✏️ type: docs 📖 +3
   

[albert-schilling]

I don't understand why Danger should not be allowed as a kind for the IconButton. We use it a lot in our app. For example for delete buttons or any kind of IconButton that does something destructive.