Rename ublock zip to xpi, instead rename with gradle before unzipping

This MR fixes a bug with the F-Droid build of Ceno. F-Droid does not allow zip files to be in the build repositories, probably for security reasons. After renaming the ublock orign xpi file to a zip file (so I could unzip it with gradle), I now get an error when running the F-Droid build. For the v2.0.7 release of Ceno on F-Droid, I added a patch, so we don't need to make a special re-release of v2.0.7 just for f-droid.

However, there's no point to keep patching a repo that we control, so this MR renames the zip back to xpi and applies the patch generally so we can use it for future releases and not trigger this error in F-Droid.