Use `OrLaterOperator` when converting license expressions

[meretp]

In the current implementation the OrLaterOperatoris not used when converting license expressions from 2.3 to 3.0. There is an open issue concerning the mismatch of classes (https://github.com/spdx/spdx-3-model/issues/324) in the spdx-3-model. As soon as this is solved, we should update the conversion of license expressions.