Simplify divisions#index intro copy

Changes the introduction copy on the divisions#index from:

> A 'division' is parliamentary terminology for a 'vote' (read more...). This page shows divisions in the Australian parliament. Make sure you read the explanation about rebellions, as they may not be what you expect. 

to 

> In the Parliament of Australia votes are counted in divisions. Through these votes, elected members shape legislation and enact Government policy. Learn more...

The explanation for Rebellions is linked 'just-in-time' at the top of the rebellions column so doesn't need to be in the intro.