Testcoin tagging incomplete

[smk762]

In the coins file, there is a key / value "is_testnet": true,
It appears that this is not applied to all testcoins, for example

This requires an audit of coins to ensure those known to be test coins have been tagged appropriately.

[cipig]

TBTC is not a test coin, it's https://www.coingecko.com/en/coins/tbtc