Change [[dependencies]] => [[graph]]

[matthewrmshin]

The old [scheduling][[dependencies]] section in suite.rc becomes [scheduling][[graph]].

[hjoliver]

LGTM - seems to have got everything!

[oliver-sanders]

Two references to the [[[dependencies]]] section need to be removed, otherwise ok:

src/tutorial/furthertopics/broadcast.rst:Add the following recurrence to the ``dependencies`` section:
src/tutorial/scheduling/datetime-cycling.rst:      recurrences. Add sections under the dependencies section for these,

Note to self about the virtues of auto-documenting the API.

[oliver-sanders]

Greping for graph and depepdencies nothing stands out.