Correct license field
    
    In the previous commit, I changed the license field in order to preserve
    the conjunctive license for src/opus_encode.cpp.  Later I was directed
    to a mailing list post that clarified that it is allowed to de-duplicate
    conjunctive licenses like this.
    
    https://lists.fedoraproject.org/archives/list/legal@lists.fedoraproject.org/thread/F4MYD7U6D2ROAL3CAOHSYDL3H6TPWZOT/#AIAWQ4PWGIBI7LCDLH3DAUOUMV6M64MR