pack-protocol doc: typofix for PKT-LINE
pack-protocol doc: typofix for PKT-LINE

Everywhere else we use PKT-LINE to denote the pkt-line formatted
data, but "shallow/deepen" messages are described with PKT_LINE().

Fix them.

Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git