[libclc] Remove mention of BSD license in readme (#111371)

This seems to be an artifact from the intial import in 2012, but even if
not, folks are better off reading the LICENSE.TXT file for the full
details if they need them.

Fixes #109968

GitOrigin-RevId: 0e8555d4dbfdfeddc01dc2ecf9a9b6e804f7b645
1 file changed