unc-openpros: note the licence conversion agreement in the data card

Syncs the unc-openpros licence section on the Hub with GitHub.

The CC BY 4.0 licence line is unchanged. A note below it now says the data was originally released under CC BY-NC-SA 4.0, and that all contributors agreed to the change of licence.

**GitHub PR:**
- [tristan-deep/OpenH-RF#41](https://github.com/tristan-deep/OpenH-RF/pull/41) — unc-openpros: add license conversion agreement in README

Files changed: 1.

```
~ unc-openpros/README.md
```

unc-openpros/README.md

@@ -59,7 +59,9 @@ The affiliations include the University of North Carolina at Chapel Hill, Johns
 
 ## License / Terms of Use
 
-[Creative Commons Attribution 4.0 International (CC BY 4.0)](https://creativecommons.org/licenses/by/4.0/legalcode.en). Retain attribution and identify modifications when reusing the data.
+[Creative Commons Attribution 4.0 International (CC BY 4.0)](https://creativecommons.org/licenses/by/4.0/legalcode.en). Retain attribution and identify modifications when reusing the data. 
+
+The original license was [Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)](https://creativecommons.org/licenses/by-nc-sa/4.0/). The conversion of the license is under agreement of all the contributors.
 
 ## Intended Usage