Remove the background music code from index.html

Purpose

The purpose of this Pull Request is to fix #160

[x] This PR doesn't commit any keys, passwords, tokens, usernames, or other secrets.
[x] I have read and understood the development best practices guidelines
[x] My code follows the style guidelines of this project
[x] I have performed a self-review of my own code
[ ] I have commented my code, particularly in hard-to-understand areas
[ ] I have made corresponding changes to the documentation

## Test environment ## Learning