Fix LSP dialyzer errors due to invalid Clock type

[madlep]

Define a t() type for the Clock struct, and use it in the function signatures to fix LSP dialyzer errors. Just using the module name in place of a struct isn't valid in this situation.

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Automated comment created by PR Commenter 🤖.

[angelikatyborska]

Thank you very much! 🙌 We do have a dialyzer check running on CI, but it only checks example solutions, not the empty stub files. And for this exercise, those two happened to have an inconsistent approach to type annotations