banner: Correct history.

Banner appeared in the 6th edition of AT&T Research unit. It was
subsequently on all the Berkeley tapes, as well as PWB, System III and
System V. The PWB/AT&T and BSD banner programs were different, and the
current FreeBSD banner program shares many elements of the 3BSD one,
though the font has changed.

Sponsored by: Netflix

(cherry picked from commit b77e235dd52a682c11ddd93256b3848cdc6f1d72)