SCCP 18: Decrease Collateralisation Ratio to 700%

[RewKang]

Simple Summary
Decrease the target Collateralisation Ratio for SNX stakers to 700%.

Abstract
There is currently a deficit of Synths (relative to demand) in the Synthetix ecosystem. Decreasing the target Collateralisation Ratio will cause some SNX stakers to increase amount of synths minted

Motivation
The Synth pegs (both sETH on Uniswap and sUSD on Curve) are off-peg. This means demand for Synths is high. There are currently other levers in the works that should contribute to tightening these pegs, but one such lever is the Collateralisation Ratio