fix: upgrade @umbraco-cms/backoffice from 16.3.2 to 16.4.0

Snyk has created this PR to upgrade @umbraco-cms/backoffice from 16.3.2 to 16.4.0.

See this package in npm:
@umbraco-cms/backoffice

See this project in Snyk:
https://app.snyk.io/org/jcdcdev/project/a4ae3923-34f4-4f49-b69c-28f319b7fe6f?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot