feat(webkit): roll WebKit to r1306 (#2899)

aslushnikov · web-flow · commit 21807bcd3527 · 2020-07-10T16:05:43.000-07:00
r1306 was built with the new slim JHBUILD procedure. If this passes
our CI bots, it'll be good to go.
diff --git a/browsers.json b/browsers.json
@@ -11,7 +11,7 @@
     },
     {
       "name": "webkit",
-      "revision": "1305"
+      "revision": "1306"
     }
   ]
 }
