[DOCS] extend create_application_emoji docs

[tom-jm69]

Summary

This pull request updates the documentation to clarify that the emoji name must be between 2 and 32 characters long. The previous documentation did not specify the maximum length for the emoji name.

Checklist

• If code changes were made, they have been tested.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, ...).

[tom-jm69]

Traceback (most recent call last):
  File "/app/cogs/utils.py", line 146, in uplemoji
    await self.bot.create_application_emoji(name=emoji_name, image=f.read())
  File "/usr/local/lib/python3.12/site-packages/discord/client.py", line 3195, in create_application_emoji
    data = await self.http.create_application_emoji(self.application_id, name, img)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/discord/http.py", line 762, in request
    raise HTTPException(response, data)
discord.errors.HTTPException: 400 Bad Request (error code: 50035): Invalid Form Body
In name: Must be between 2 and 32 in length.