FIX: incorrect symbol for Asset ARB in Arbitrum

[Thorian1te]

current declaration for asset arb.. symbol: 'ARB' is incorrect it should be ETH.

export const AssetARB: Asset = { chain: ARBChain, symbol: 'ARB', ticker: 'ETH', synth: false }

ARB.ARB-0X912CE59144191C1204E64559FE8253A0E49E6548 arb.arb is a token on arbitrum.

maybe we can name it. just a suggestion.

export const AssetAETH: Asset = { chain: ARBChain, symbol: 'ETH', ticker: 'ETH', synth: false }