Update emojis so all are visible regardless of dark/light theme

Certain emojis are basically impossible to see in dark mode. For example, 🔜®️➰➕ and other heavy math symbols have no outline and are almost exactly the same color as the dark theme background, making them extremely difficult to see. Here's a screenshot showing how difficult it is to see these. There are multiple symbols after the numbers on each of those lines that you have to look very very closely to see. Given Discord defaults to the dark theme, it is baffling to me that the default Discord experience with these emojis is an accessibility nightmare. Simply changing the color to one that shows up or at least contrasts with both light and dark theme backgrounds, or adding a lighter outline to these would greatly improve readability.