fix cargo features type signature

[daeho-ro]

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Type fix, I was originally added Symbol type but it is no longer exist.

[Copilot]

Pull request overview

Updates the Sorbet type signature for the public Formula#std_cargo_args helper to change what types are accepted for the features: parameter.

Changes:

• Adjust std_cargo_args’s features: Sorbet signature to no longer include Symbol.

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