Update LICENSE

LICENSE

@@ -1,10 +1,10 @@
 DepthDif GeoTIFF Raster and Aligned ARGO Dataset
 Dataset license notice
 
-SPDX-License-Identifier: CC-BY-2.0
+SPDX-License-Identifier: CC-BY-4.0
 
 This dataset package is released by the DepthDif contributors under the
-Creative Commons Attribution 2.0 International license (CC BY 2.0).
+Creative Commons Attribution 4.0 International license (CC BY 4.0).
 
 You may share and adapt this dataset package, including for commercial use,
 provided that you give appropriate credit, provide a link to the license, and