Update license-mapping.json for BSD-3-Clause

[italvi]

BSD-3-Clause and BSD-4-Clause both had the name "BSD License", s.t. an unique mapping was not possible. The BSD-4-Clause is the "original" BSD-Clause, while BSD-3 is the "2.0". Therefore, I changed the name "BSD License" for the BSD-3-Clause to "BSD License 2.0".

[sschuberth]

I agree that "BSD License" should not be mapped to "BSD-3-Clause" as it's not clear which BSD version is meant in the former (we did remove this mapping in ORT a while a go, BTW).

However, I'm not sure whether mapping "BSD License 2.0" instead is a good idea, as it could easily be misread as "BSD License 2", which in turn could be misread as "BSD-2-Clause". I acknowledge that Wikipedia mentions "BSD License 2.0" as an alias for "BSD-3-Clause", but I'm wondering whether there's any real-life example of a software package that uses "BSD License 2.0" as part of its license metadata?

[jeremylong]

"BSD License 2.0" is used: https://sourcegraph.com/search?q=context:global+content:%22BSD+License+2.0%22&patternType=keyword&sm=0

[chadlwilson]

Rather than further debate about usage of variants, the generic name was removed from 3-Clause in #994 so it's no longer mapped to both 3-Clause (new/modified/revised) and 4-Clause (original)

So this PR is probably surplus to requirements now.