FIX DMN schema generation

[gitgabrio]

Fix

   if (t.getTypeConstraint() != null && !t.getTypeConstraint().isEmpty()) {
            parseSimpleType(DMNOASConstants.X_DMN_TYPE_CONSTRAINTS, t, schema, t.getTypeConstraintFEEL(), t.getAllowedValues());
    }

inside org.kie.dmn.openapi.impl.DMNTypeSChema.
Eventually fix returned empty enum

"tCollection": {
            "type": "array",
            "items": {
                "enum": [],