[Doc Update] Change Mumbai to Amoy

[mrodriguez3313]

Mumbai chain is now deprecated, People are having issues adding the borg token to their mobile wallets. As well as on desktop

EDIT: Resources for update:

• https://support.polygon.technology/support/solutions/articles/82000907114-how-to-add-amoy-network-in-your-wallet-
• After adding AMOY to desktop, use this link to follow BORG https://docs.metamask.io/wallet/reference/wallet_watchasset/?type=ERC20&options%5Baddress%5D=0x99a8b2B50c4bFBf916Add5DFdf680fc873FA81f4&options%5Bsymbol%5D=BORG&options%5Bdecimals%5D=18&options%5Bimage%5D=https://raw.githubusercontent.com/functionland/sugarfunge-explorer/master/assets/BORG.svg&options%5BtokenId%5D=BORG