Fix to typo in project "Build a Pomodoro App with HTML, CSS, JavaScript"

[MilanGrujicic]

Closes #issue

• [ ] My project tutorial topic has already been approved by the Codédex team.
• [ ] My project tutorial file renders properly in mdx.
• [ ] My .mdx file follows the project template, as well as what's recommended in the content guidelines.
• [ ] The content written is my own, and not plagiarized from other sources.
• [ ] All code written is thoroughly functional and commented (or documented).
• [ ] I have already completed a self-review of the project tutorial.
• [ ] I will comply with changes made or recommended by the Codédex team about my project tutorial.

[MilanGrujicic]

FYI, this PR is linked to that 👉 issue 👈.

[sonnynomnom]

I'm going to close one but won't deduct points!