Add note about transaction fees

[snaveoguh]

Description

This adds a final bullet point under the 3 existing for "Requirements for Replace Artwork proposal:" and highlights to the user that it could incur serious gas fees. The bullet point is bold/red to warn the user.

Motivation & context

This will help future DAO members understand the high gas fees associated with both proposing and executing a transaction to repalce the artwork.

Code review

Should be fairly straightforward - a basic addition of a singular bullet point.

Type of change

Provides more context to a user before they initiate a costly trait update proposal.

Checklist

• I have done a self-review of my own code
• Any new and existing tests pass locally with my changes
• My changes generate no new warnings (lint warnings, console warnings, etc)

[vercel]

Someone is attempting to deploy a commit to the Nouns Builder Team on Vercel.

A member of the Team first needs to authorize it.

[snaveoguh]

Reach me on Discord @borg00000