feat(token-list): update the btt token info

[Benson0224]

Update the old btt token name to BTTOLD.

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After review, we found that the old BTT token was also included in the "pancakeswap-top-100.json" list, but the token name is not correct. so we raised a new PR to change the token name of old BTT as BTTOLD, as a continuation of #401

Otherwise, it may confuse the users, please help to review and merge it, thanks.

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[Chef-Cheems]

Thanks for the PR! 🙂