FF151 @media rule picture-in-picture value supported (#29534)

* FF151 @media rule picture-in-picture value supported

* Apply suggestion from @hamishwillee

Author: hamishwillee

css/at-rules/media.json

@@ -818,8 +818,7 @@
                 },
                 "edge": "mirror",
                 "firefox": {
-                  "version_added": "preview",
-                  "impl_url": "https://bugzil.la/1858562"
+                  "version_added": "151"
                 },
                 "firefox_android": "mirror",
                 "oculus": "mirror",
@@ -834,7 +833,7 @@
                 "webview_ios": "mirror"
               },
               "status": {
-                "experimental": true,
+                "experimental": false,
                 "standard_track": true,
                 "deprecated": false
               }