fix(transaction-update): replace ethereumjs-util with @ethereumjs/util

[legobeat]

Description

ethereumjs-util is deprecated and maintained as @ethereumjs/util as of v8. metamask-institutional is already using the newer version, except in one place.

The only outstanding usage has been migrated to @ethereumjs/util and legacy ethereumjs-util has been removed.

Motivation and Context

How Has This Been Tested?

Not at all.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.