etc: Remove unnecessary quotes in .desktop (#5540)

etc/linux-desktop/syncthing-ui.desktop

@@ -1,7 +1,7 @@
 [Desktop Entry]
 Name=Syncthing Web UI
 GenericName=File synchronization UI
-Comment="Opens Syncthing's Web UI in the default browser (Syncthing must already be started)."
+Comment=Opens Syncthing's Web UI in the default browser (Syncthing must already be started).
 Exec=/usr/bin/syncthing -browser-only
 Icon=syncthing
 Terminal=false