git.plugin.zsh: Don't run Git hooks when making a WIP commit (#4751)

When making a WIP commit, we generally just want to save the state of the
current branch temporarily, maybe because we want to push our work for backup
purposes, or change branch to work on something else. Therefore, it's generally
undesirable to run Git hooks, which might do things like run linters, because
we probably don't care if our WIP has lint errors.