devel/jujutsu: update to version 0.40.0

For the complete list of changes see:

https://github.com/jj-vcs/jj/releases/tag/v0.40.0

In addition to the version upgrade the following changes were applied
to this port, based on suggestions received from Theo Buehler, the
maintainer of the devel/jujutsu port on OpenBSD:

• Add a run dependency on git
• Point at the documetation of this release, not "latest"
• Change the defaault editor from nano to vi
• Install shell completion files for bash, fish, and zsh
• Install man-pages