Increase icon size for categories in emoji picker

What does this MR do and why?

Since we updated our SVGs to be lighter, the icons for emoji categories seem to be a little to small. By increasing their size, their easier to distinguish.

Screenshots

Before	After

How to set up and validate locally

Visit e.g. an issue page and add an award emoji

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #348790 (closed)