Drop another old workaround (KDE package signature check)

It seems Rawhide auto-signing is working fine now: openQA claims
this needle has 'never' been matched (which really means 'not
for a long time'), and I can't find any test fail in the last
year which looks like it landed on this 'authenticate' screen
but the needle failed to match, or anything like that.

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

needles/kde/desktop_package_tool_update_authenticate.json

@@ -1,16 +0,0 @@
-{
-  "properties": [],
-  "area": [
-    {
-      "xpos": 254,
-      "ypos": 167,
-      "width": 71,
-      "height": 61,
-      "type": "match"
-    }
-  ],
-  "tags": [
-    "DESKTOP-kde",
-    "desktop_package_tool_update_authenticate"
-  ]
-}

tests/desktop_update_graphical.pm

@@ -87,20 +87,8 @@ sub run {
         boot_to_login_screen;
     }
     else {
-        # KDE will prompt for authentication if any package is not
-        # signed. As of 2016-09-23, puiterwijk claims Rawhide packages
-        # will be autosigned 'by Monday', so if this happens, we're
-        # going to treat it as a soft fail, indicating the update
-        # mechanism works, but a package that should have been signed
-        # was not.
-        assert_screen ['desktop_package_tool_update_done', 'desktop_package_tool_update_authenticate'], 180;
-        if (match_has_tag('desktop_package_tool_update_authenticate')) {
-            record_soft_failure;
-            type_very_safely get_var('USER_PASSWORD', 'weakpassword');
-            send_key 'ret';
         assert_screen 'desktop_package_tool_update_done', 180;
     }
-    }
     # back to console to verify updates
     $self->root_console(tty=>3);
     verify_updated_packages;