[DOC] Replace invalid emojis

Created by: Razer6

What does this MR do?

This PR replaces invalid emojis. Additionally it links to the emoji cheatsheet on dropbox @dosire Is that ok? Point to the original cheatsheet doesn't make sense, because the symbols are quite different.

Why was this MR needed?

With the switch to the Phantom Open emoji library, not all emojis are valid anymore and aren't shown properly anymore.

Screenshots

Before

After