[PATCH] lib: update notmuch_tags_get examle to reflect api change

[Austin Clements]

LGTM.

On Mon, 30 Jan 2012 09:05:15 -0500, Allan Wind <allan_wind at lifeintegrity.com> wrote:
> The function notmuch_database_find_message_by_filename now requires a
> notmuch_message_t and returns a notmuch_status_t.  This
> change was introduced with 02a3076711, LIBNOTMUCH_VERSION_MAJOR = 2,
> version 0.9.