Drop unused branch and needle in desktop_login

We never hit this path without a system menu button any more,
due to changes in KDE over time. It hasn't been hit for two years.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/kde/reboot_icon.json

@@ -1,15 +0,0 @@
-{
-  "area": [
-    {
-      "height": 38,
-      "type": "match",
-      "width": 39,
-      "xpos": 449,
-      "ypos": 610
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "reboot_icon"
-  ]
-}

tests/desktop_login.pm

@@ -144,9 +144,7 @@ sub switch_user {
 }
 
 sub reboot_system {
-    # Reboots the system and handles everything until the next GDM screen.
+    # Reboots the system and handles everything until the next login screen.
-    if (check_screen "system_menu_button") {
-        # In a logged in desktop, we access power options through system menu
     assert_and_click "system_menu_button";
     # In KDE the reboot entry is right here, on GNOME we need to
     # enter some kind of power option submenu.
@@ -154,12 +152,6 @@ sub reboot_system {
     click_lastmatch;
     assert_and_click "reboot_entry" if (match_has_tag("power_entry"));
     assert_and_click "restart_confirm";
-    }
-    # When we are outside KDE (not logged in), the only way to reboot is to click
-    # the reboot icon.
-    else {
-        assert_and_click "reboot_icon";
-    }
     boot_to_login_screen();
 }