Wrong SPDX identifier for older Creative Commons Attribution-ShareAlike licenses

[nicoroeser]

The Other conformant licenses section in the Conformant Licenses list has a wrong SPDX identifier for the superseded licenses in the Creative Commons Attribution-ShareAlike family. Probably due to a copy-and-paste mistake.

The mentioned SPDX identifier should include CC-BY-SA- instead of CC-BY-.

[mlinksva]

Embarrassing, thanks so much for catching and fixing!