archive/tar: spell license correctly in example
archive/tar: spell license correctly in example

Change-Id: Ice85d161f026a991953bd63ecc6ec80f8d06dfbd
Reviewed-on: https://go-review.googlesource.com/17901
Run-TryBot: Joe Tsai <ad9e03fbec35106ba742f446a098eef3d5e31d20@digital-static.net>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

vbatts/tar-split