update eletron to v42 (#4144)

additional things:
- removed fix chrome-sandbox permissions (runs without)
- added `npx install-electron` which downloads the electron binaries

new in v42: 

> Electron now downloads its binary into node_modules dynamically on
first launch instead of running a postinstall script. Added the
install-electron script to manually trigger the download as well.
electron/electron#49328

Author: khassel

.github/workflows/automated-tests.yaml

@@ -64,9 +64,8 @@ jobs:
           npx playwright install --with-deps chromium
       - name: "Prepare environment for tests"
         run: |
-          # Fix chrome-sandbox permissions:
-          sudo chown root:root ./node_modules/electron/dist/chrome-sandbox
-          sudo chmod 4755 ./node_modules/electron/dist/chrome-sandbox
+          # Download electron binary
+          npx install-electron
           # Start labwc
           WLR_BACKENDS=headless WLR_LIBINPUT_NO_DEVICES=1 WLR_RENDERER=pixman labwc &
           touch config/custom.css