How do I uninstall Wine?
An uninstaller doesn't exist for this app (Wine Staging 2.0-rc3).

The pkg file itself only installs Wine Staging.app to /Applications, which is self-contained and you can simply delete it.

Almost anything else like user installed apps or libraries reside in the folder $USER/.wine and you can simply delete it. Some files are also added in $USER/.local/*/ or $USER/.config/*/. The .local and .config folders may also be used by other apps like X11 or Wireshark. Here are some directories you may find preferences and other cruft.

~/.config/menus/applications-merged/wine-*
~/.local/share/applications/wine/
~/.local/share/desktop-directories/wine-*
~/Library/Application\ Support/Wine