Fix GPU case impl url

Author: hamishwillee

api/GPU.json

@@ -35,7 +35,10 @@
           "firefox": [
             {
               "version_added": "147",
-              "impl_url": "https://bugzil.la/2004105",
+              "impl_url": [
+                "https://bugzil.la/2004105",
+                "https://bugzil.la/1942431"
+              ],
               "partial_implementation": true,
               "notes": "Supported on Windows and macOS on Apple silicon, in all contexts except for service workers."
             },