fix: clean Signal and Browser dependencies

- libgtk4-1 is not used by Signal and now it declares the libgtk3-0
  as a dependency;
- Zenity is not needed as a file manager once Thunar is used;
- ATK is installed for Signal but not for any apps, remove until there
  is a shared formula or pillar to install accessibility tools; and
- Ayatana AppIndicator for tray widget. Signal tray widget is buggy,
  sometimes quitting doesn't quit and there is no configuration option
  to start the tray, only command-line option. Because of these reasons,
  not enabling the tray bar was chosen.

salt/browser/install-common.sls

@@ -21,7 +21,6 @@ include:
       - qubes-core-agent-networking
       - ca-certificates
       - qubes-core-agent-thunar
-      - zenity
 
 {% set pkg = {
   'Debian': {

salt/signal/install.sls

@@ -25,10 +25,7 @@ include:
       - qubes-core-agent-thunar
       - thunar
       - signal-desktop
-      - zenity
       - dunst
-      - libatk1.0-0
-      - libatk-bridge2.0-0
-      - libgtk-4-1
+      - libayatana-appindicator3-1
 
 {% endif -%}