Update `post-leetcode-potd-to-discord` README example message

See https://github.com/code-chronicles-code/leetcode-curriculum/blob/main/workspaces/post-leetcode-potd-to-discord/README.md and compare with this live message:

<img width="560" alt="Screen Shot 2024-09-29 at 09 13 07" src="https://github.com/user-attachments/assets/9f05da9a-ef4d-4b1d-bd67-46a3d11aa5db">
