notes: avoid empty line in template

notes: avoid empty line in template

When `git notes` prepares the template it adds an empty newline between
the comment header and the content:

>
> #
> # Write/edit the notes for the following object:
>
> # commit 0f3c55d4c2b7864bffb2d92278eff08d0b2e083f
> # etc

This is wrong structurally because that newline is part of the comment,
too, and thus should be commented. Also, it throws off some positioning
strategies of editors and plugins, and it differs from how we do commit
templates.

Change this to follow the standard set by `git commit`:

>
> #
> # Write/edit the notes for the following object:
> #
> # commit 0f3c55d4c2b7864bffb2d92278eff08d0b2e083f
>

Tests pass unchanged after this code change.

Signed-off-by: Michael J Gruber <git@grubix.eu>
Signed-off-by: Taylor Blau <me@ttaylorr.com>