If the code is not referred to in your source code, the dependency will be dropped. Also, to clarify, the dependency is on deepbook V2, which is a system package (and is now deprecated) not Deepbook v3, the version that is currently in use. This is happening as a side effect of the new mechanism for automatically managing dependencies on system packages.

To disable implicit Deepbook dependencies in Sui v1.45+, don’t include Deepbook in [dependencies] in Move.toml.

To disable Deepbook's implicit dependencies added since Sui v1.45, set implicit-deps = false in your Move.toml under the [package] section.