Reorder a note section in aria2c.rst

[ardecvz]

Hello,

I've reordered one note section in aria2c.rst to match the existing placement of notes after the corresponding options.

Thank you Tatsuhiro, Nils (for deprecated DownThemAll! too) and others for the amazing piece of software!

[tatsuhiro-t]

Thank you for PR.
I confirm that the current position is wrong. And I think the correct position is under --file-allocation option. Could you make this change? It is fine for us to do it ourselves.
The translated versions are maintained by collaborators, and normally we just edit English version only.

[ardecvz]

Rebased under --file-allocation option and without translations.

Of course, you could change it further yourself if you'll find more suitable position.

[tatsuhiro-t]

Thank you. LGTM!