chore: Update flatpak configuration and install scripts

Author: mr-cheffy

flatpak/io.github.zen_browser.zen.yml.template

@@ -27,7 +27,7 @@ modules:
     build-commands:
       - mv zen /app/
 
-      - install -Dm0755 metadata/launch-script.sh ${FLATPAK_DEST}/bin/launch-script.sh
+      - install -Dm0755 metadata/launch-script.sh ${{FLATPAK_DEST}}/bin/launch-script.sh
       - install -Dm0644 metadata/policies.json ${{FLATPAK_DEST}}/bin/distribution/policies.json
       - install -Dm0644 metadata/icons/io.github.zen_browser.zen.png ${{FLATPAK_DEST}}/share/icons/hicolor/256x256/apps/${{FLATPAK_ID}}.png
       - install -Dm0644 metadata/io.github.zen_browser.zen.metainfo.xml ${{FLATPAK_DEST}}/share/metainfo/${{FLATPAK_ID}}.metainfo.xml