Fix accounts bug inside 8.md

[diranl]

Bug explanation:

The web3.eth.accounts isn't an array as the code expects but a series of functions as per https://web3js.readthedocs.io/en/1.0/web3-eth-accounts.html

Instead, the correct implementation ought to use web.eth.getAccounts as per https://web3js.readthedocs.io/en/1.0/web3-eth.html#getaccounts

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[eduardonunesp]

Thanks @diranl, do you mind to accept the terms on check boxes?

[diranl]

Done