Fix: Firefox status for prefers-reduced-motion

This feature is not tracked in Chrome or Firefox platform status.

* Firefox Windows bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1365045
* Firefox macOS bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1475462 

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Fix #647

Author: JamesCatt

status.json

@@ -5495,6 +5495,10 @@
       "text": "Shipped",
       "value": 1
     },
+    "ff_views": {
+      "text": "Shipped",
+      "value": 1
+    },
     "uservoiceid": 19291531,
     "statusid": 321
   },