Policy Significance- Code 3 withdrawn

[PetyaKangalova]

Checked with the OECD DAC and it looks like Policy Significance 3 has been discountinued.

This is the message I got from the OECD DAC.

Yes, score 3 for desertification has been discontinued between 2016 and 2018. We do not have a document certifying that but it was not very used and systematically replaced by 2 for analysis.

Looking at this paper (page 10), it say:
The desertification marker initially allowed scoring also with the additional value “3”, used to identify activities with the “principal objective and in support of an action programme” 23. The score “3” was seldom used and it was discontinued.

As such, I suggest we mark as "withdrawn" to reflect that change. Will add a seperate pull request for this.