fix: Remove innerHTML sink in Palindrome Checker

[sylwia-budzynska]

Checklist:

• [x] I have read freeCodeCamp's contribution guidelines.
• [x] My pull request has a descriptive title (not a vague title like Update index.md)

Closes #XXXXX

Please also see an email I sent to possible-security-issue at freecodecamp dot org.

Interpolating user input into innerHTML sink can lead to security issues.

This pull request changes the innerHTML sink to innerText in the Palindrome Checker project, which fixes the vulnerability.

This is my first contribution to freeCodeCamp, let me know if anything could be improved! I also wanted to extend my thanks to the freeCodeCamp team for creating such a great learning platform 🙌

[raisedadead]

:sparkles: :sparkles: AWESOME! :sparkles: :sparkles:

LGTM.

Thanks for this pull request and for contributing to the codebase for the first time. We will be looking forward to more contributions in the future.

Happy contributing.