cask_loader: do not auto-tap in FromTapLoader

[nandahkrishna]

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This PR aims to fix #10584, by removing auto-tapping from cask's FromTapLoader.

Output:

➜ brew info mongodb/brew/mongodb-community
Error: No available formula or cask with the name "mongodb/brew/mongodb-community".
Please tap it and then try again: brew tap mongodb/brew

➜ brew info --formula mongodb/brew/mongodb-community
Error: No available formula with the name "mongodb/brew/mongodb-community".
Please tap it and then try again: brew tap mongodb/brew

➜ brew info --cask mongodb/brew/mongodb-community
Error: Cask 'mongodb/brew/mongodb-community' is unavailable.
Please tap it and then try again: brew tap mongodb/brew

[BrewTestBot]

Review period will end on 2021-03-12 at 15:43:18 UTC.

[BrewTestBot]

Review period skipped due to critical label.

[MikeMcQuaid]

Thanks @nandahkrishna !