Extend CC-BY-4.0 scope to training and validation sets

LICENSE

@@ -8,7 +8,14 @@ A. CC-BY-4.0
 --------------------------------------------------------------------------
 Applies to: alpha_05_4071_2024, alpha_05_4071_4048, alpha_15_13929_2024,
 alpha_15_13929_4048, AR_1_Ret_360, AR_3_Ret_360, AR_14_Ret_180,
-NASA_2DWMH, NASA_2DZP, NASA_2DN00, NASA_ASJ, NASA_FaithHill.
+NASA_2DWMH, NASA_2DZP, NASA_2DN00, NASA_ASJ, NASA_FaithHill,
+and every case under data/train/ and data/validation/.
+
+The training and validation sets are drawn from the same upstream sources as
+the CC-BY-4.0 test cases: the Xiao et al. parametric periodic-hill database,
+the Vinuesa duct database, and the CBFS and periodic-hill reference flows of
+the v1 benchmark. None of them derive from ERCOFTAC kbwiki material, so none
+fall under section B.
 
 Upstream sources are public-domain or CC-BY: NASA Turbulence Modeling
 Resource, the Vinuesa duct database, and the Xiao parametric periodic-hill