fix(node-workspace): maintain the dependency version prefix in newCandidate

[OrKoN]

In #1723 I overlooked that prefix is also generated in the newCandidate as I incorrectly assumed that that method is only invoked for new packages. It's actually invoked for new updated of any package.

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #1723 🦕