Disable AppImage update check of Official Deezer channel

[randshell]

The Electron AppImage that we build attempts to check for updates using the Official Deezer Channel, which only supports Windows and possibly MacOS.

This patch disables the update check for Linux systems, however in the future we could revert this and implement our own update logic to support our own self-updating AppImages.

Example logs:

18:50:30.378 › Init App
Checking for update
Error: Error: This file could not be downloaded, or the latest version (from update server) does not have a valid semver version: "undefined"
    at Object.newError (/tmp/.mount_deezerGgAVl2/resources/app.asar/node_modules/electron-updater/node_modules/builder-util-runtime/src/index.ts:56:17)
    at AppImageUpdater.isUpdateAvailable (/tmp/.mount_deezerGgAVl2/resources/app.asar/node_modules/electron-updater/src/AppUpdater.ts:321:13)
    at AppImageUpdater.doCheckForUpdates (/tmp/.mount_deezerGgAVl2/resources/app.asar/node_modules/electron-updater/src/AppUpdater.ts:378:22)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
18:50:50.759 (main/warn) ›  Error: This file could not be downloaded, or the latest version (from update server) does not have a valid semver version: "undefined"
    at Object.newError (/tmp/.mount_deezerGgAVl2/resources/app.asar/node_modules/electron-updater/node_modules/builder-util-runtime/src/index.ts:56:17)
    at AppImageUpdater.isUpdateAvailable (/tmp/.mount_deezerGgAVl2/resources/app.asar/node_modules/electron-updater/src/AppUpdater.ts:321:13)
    at AppImageUpdater.doCheckForUpdates (/tmp/.mount_deezerGgAVl2/resources/app.asar/node_modules/electron-updater/src/AppUpdater.ts:378:22)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)