Use latest tanuki_emoji gem

What does this MR do and why?

Extracts the backend changes from Update to Unicode 15.1 emojis from tanuki_emoji... (!166790 - merged).

This updates the code to use the latest tanuki_emoji gem, which supports Unicode 15.1 emojis.

Related to #493945 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

1. start a Rails console, and enter the following

   TanukiEmoji.find_by_alpha_code('t_rex')

   You should get back the t_rex emoji, which is part of the new gem

   #<TanukiEmoji::Character: 🦖 (1f996), alpha_code: ":t_rex:", aliases: [], name: "t_rex", description: "T-Rex">

2. Enter

   Banzai.render(':t_rex:', project: nil)

   This will render into html the new <gl-emoji> for the t_rex emoji.

   <p data-sourcepos="1:1-1:7" dir="auto"><gl-emoji title="T-Rex" data-name="t_rex" data-unicode-version="10.0">🦖</gl-emoji></p>

3. Note, however, that if you use from the web, such as an issue comment, what is displayed is a grey question mark image. This is because the frontend has not yet been upgraded, so it doesn't understand the new emojis. But this is expected.

4. Notice that emoji autocomplete, and the emoji picker, continue to use the older data. For a reference, the new emoji picker looks like what is detailed in !166790 (merged)