Move box_shadow_inset_bg.html to wpt reftests.

tests/ref/basic.list

@@ -22,7 +22,6 @@ flaky_cpu == append_style_a.html append_style_b.html
 == box_shadow_border_box_a.html box_shadow_border_box_ref.html
 == box_shadow_default_color_a.html box_shadow_default_color_ref.html
 == box_shadow_inset_a.html box_shadow_inset_ref.html
-== box_shadow_inset_bg.html box_shadow_inset_bg_ref.html
 == box_shadow_inset_parsing_a.html box_shadow_inset_parsing_ref.html
 == box_shadow_spread_a.html box_shadow_spread_ref.html
 == canvas_radial_gradient_a.html canvas_radial_gradient_ref.html

tests/wpt/mozilla/meta/MANIFEST.json

@@ -779,6 +779,18 @@
             "url": "/_mozilla/css/border_spacing_a.html"
           }
         ],
+        "css/box_shadow_inset_bg.html": [
+          {
+            "path": "css/box_shadow_inset_bg.html",
+            "references": [
+              [
+                "/_mozilla/css/box_shadow_inset_bg_ref.html",
+                "=="
+              ]
+            ],
+            "url": "/_mozilla/css/box_shadow_inset_bg.html"
+          }
+        ],
         "css/box_shadow_paint_order_a.html": [
           {
             "path": "css/box_shadow_paint_order_a.html",
@@ -5208,6 +5220,18 @@
           "url": "/_mozilla/css/border_spacing_a.html"
         }
       ],
+      "css/box_shadow_inset_bg.html": [
+        {
+          "path": "css/box_shadow_inset_bg.html",
+          "references": [
+            [
+              "/_mozilla/css/box_shadow_inset_bg_ref.html",
+              "=="
+            ]
+          ],
+          "url": "/_mozilla/css/box_shadow_inset_bg.html"
+        }
+      ],
       "css/box_shadow_paint_order_a.html": [
         {
           "path": "css/box_shadow_paint_order_a.html",

tests/wpt/mozilla/tests/css/box_shadow_inset_bg.html

@@ -1,3 +1,4 @@
+<link rel='match' href='box_shadow_inset_bg_ref.html'>
 <div></div>
 
 <style>