dawn.json: Removed unused "face" bitmask

It was replaced by "cull mode" but we forgot to remove it.

BUG=dawn:22

Change-Id: I2195ed64d1df05b01baf37d477a2a7cc6cf1156c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/9200
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

dawn.json

@@ -547,15 +547,6 @@
             {"name": "depth", "type": "uint32_t"}
         ]
     },
-    "face": {
-        "category": "bitmask",
-        "values": [
-            {"value": 0, "name": "none"},
-            {"value": 1, "name": "back"},
-            {"value": 2, "name": "front"},
-            {"value": 3, "name": "both"}
-        ]
-    },
     "fence": {
         "category": "object",
         "methods": [