Remove 'category' as a field type for action forms (#29133)

docs/actions/custom.md

frontend/src/metabase-types/api/actions.ts

...se/actions/components/ActionForm/ActionForm.unit.spec.tsx

...e/actions/components/ActionForm/ActionFormFieldWidget.tsx

...etabase/actions/components/ActionForm/FormFieldEditor.tsx

...tions/components/ActionForm/FormFieldEditor.unit.spec.tsx

frontend/src/metabase/actions/components/ActionForm/utils.ts

...actions/containers/ActionCreator/FormCreator/constants.ts

...ase/actions/containers/ActionCreator/FormCreator/utils.ts

...nd/src/metabase/actions/containers/ActionCreator/utils.ts

frontend/src/metabase/actions/utils.ts

frontend/src/metabase/actions/utils.unit.spec.ts

frontend/src/metabase/entities/actions/constants.ts