fix: correct fromHex function documentation

[Fibonacci747]

Fix incorrect documentation for fromHex function:

Why it was wrong:

• Referenced non-existent type "ThrowType::DontThrow" instead of "WhenError::DontThrow"
• Claimed function "replaces bad hex characters with 0's" which never happened

Why it's now correct:

• Uses correct enum type "WhenError::DontThrow"
• Accurately describes behavior: "returns an empty bytes array on any validation error"
• Documentation now matches actual implementation and test expectations

[github-actions]

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[clonker]

Thanks, it seems the docstring was a bit dated here!