use calf plugins extension from flathub

[Bleuzen]

related to: https://github.com/flathub/com.github.wwmm.easyeffects/issues/169

Currently this results in duplicate warnings since upstream EE still bundles the calf plugins. EE has to be updated after this is merged: https://github.com/wwmm/easyeffects/pull/2074 (or alternatively a temporary patch has to be created to remove calf plugins from easyeffects/util/flatpak/easyeffects-modules.json)

[flathubbot]

Started test build 17460

[flathubbot]

Build 17460 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/85/com.github.wwmm.easyeffects.flatpakref

[vchernin]

superseeded by #171