Adjust warning_bar needle so LibreOffice ad doesn't match it

https://openqa.fedoraproject.org/tests/117131 shows a spurious
match of the anaconda warning_bar needle - it's matching in an
ad for LibreOffice. Add a bit of the grey above the bar, so
hopefully this won't happen any more.

needles/anaconda/universal/warning_bar.json

@@ -1,11 +1,11 @@
 {
     "area": [
         {
-            "height": 20,
+            "height": 30,
             "type": "match",
             "width": 414,
             "xpos": 283,
-            "ypos": 741
+            "ypos": 726
         }
     ],
     "properties": [],
@@ -13,4 +13,4 @@
         "ENV-DISTRI-fedora",
         "anaconda_warning_bar"
     ]
-}
+}