Fix typo in joinStrings-example.spec.js test

[aakarsh-dev-commits]

Corrected the last name used in the example for accuracy.

Because

The original example contained an incorrect last name, which may cause confusion for learners. This PR corrects the last name for accuracy.

This PR

• Fixes a typo in the example within joinStrings-example.spec.js by correcting the last name.

Issue

Additional Information

Pull Request Requirements

• I have thoroughly read and understand The Odin Project Contributing Guide
• The title of this PR follows the location of change: brief description of change format, e.g. 01_helloWorld: Update test cases
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If this PR includes any changes that affect the solution of an exercise, I've also updated the solution in the /solutions folder