Automate plist version setting on MacOS
We should add a sed line or some other processing step on the Info.plist file for the MacOS bundles, so we don't have to remember to manually update the plist version each release.
$TORBROWSER_VERSION should be available in gitian/descriptors/mac/gitian-bundle.yml. If we change the version in the plist to be VERSION, we should be able to sed the plist with the actual version easily enough.