Avoid re-evaluation of the key input in restore implementation

[itchyny]

Description

This PR fixes the re-evaluation of the key input for setting the cache-hit output in the restore implementation.

Motivation and Context

I noticed that the restore implementation re-evaluates the key input on setting the cache-hit output.
This does not cause any real issue, the change just refactors the code.

How Has This Been Tested?

I have run the unit tests restoreImpl.test.ts which covers the code I changed.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (add or update README or docs)
• Refactoring (non-breaking change which does not change the behavior)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.