Clean up wallpaper needles a bit

The backgrounds we have are F30 backgrounds, not F31: there are
no F31 backgrounds yet, F31 images are using F30 backgrounds
(which is a bug we should file). Also we really only need one
F30 background needle to match both KDE and GNOME if we pick a
sensible area of the screen to use, and let's use one that has
a bit more contrast for safer matching.

Note: F30 background is *meant* to be animated, but in fact
neither GNOME nor KDE seems to use the animated version by
default. Which makes our lives easier! Sucks for whoever put in
the work to animate it, though.

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

needles/anaconda/identification/30_wallpaper-20190527.json

@@ -1,15 +0,0 @@
-{
-  "area": [
-    {
-      "xpos": 838,
-      "ypos": 663,
-      "width": 163,
-      "height": 51,
-      "type": "match"
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "30_wallpaper"
-  ]
-}

needles/anaconda/identification/30_wallpaper.json

@@ -1,11 +1,11 @@
 {
     "area": [
         {
-      "xpos": 847,
-      "ypos": 722,
-      "width": 163,
             "height": 38,
-      "type": "match"
+            "type": "match",
+            "width": 163,
+            "xpos": 437,
+            "ypos": 672
         }
     ],
     "properties": [],

needles/anaconda/identification/31_wallpaper-20190527.json

@@ -1,15 +0,0 @@
-{
-  "area": [
-    {
-      "xpos": 838,
-      "ypos": 663,
-      "width": 163,
-      "height": 51,
-      "type": "match"
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "31_wallpaper"
-  ]
-}

needles/anaconda/identification/31_wallpaper.json

@@ -1,16 +0,0 @@
-{
-  "area": [
-    {
-      "xpos": 847,
-      "ypos": 722,
-      "width": 163,
-      "height": 38,
-      "type": "match"
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "31_wallpaper",
-    "Rawhide_wallpaper"
-  ]
-}