t3404 (rebase -i): move comment to description
t3404 (rebase -i): move comment to description

Add a comment describing the setup in t3404 to its --help output.

This should make it easier to decide where to put new functions
without disrupting the flow of the file or obstructing the description
of the test setup.

Signed-off-by: Jonathan Nieder <b57189c5f2fd5b3daf3350a77fde90def1080fa5@gmail.com>
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