Fix/setstate test

[u1001932]

Pre-Submission Checklist

• Your pull request targets the staging branch of freeCodeCamp.
• [v] Branch starts with either fix/, feature/, or translate/ (e.g. fix/signin-issue)
• [v] You have only one commit (if not, squash them into one commit).
• [v] All new and existing tests pass the command npm test. Use git commit --amend to amend any fixes.

Type of Change

• [v] Small bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds new functionality)
• Breaking change (fix or feature that would change existing functionality)
• Add new translation (feature adding new translations)

Checklist:

• Tested changes locally.
• [v] Addressed currently open issue (replace XXXXX with an issue no in next line)

Closes #18084

Description

Add test for this.setState. Requires a function to be passed to setState when a previous state is used to determine the next state, per React guideline.