Remove chromium.webkit recipe test config for win8 bot.

BUG=521704,496259

Review URL: https://codereview.chromium.org/1298003003

Cr-Commit-Position: refs/heads/master@{#343819}

testing/buildbot/chromium.webkit.json

@@ -1258,32 +1258,6 @@
       }
     ]
   },
-  "WebKit Win8": {
-    "gtest_tests": [
-      {
-        "test": "blink_heap_unittests"
-      },
-      {
-        "test": "blink_platform_unittests"
-      },
-      {
-        "test": "webkit_unit_tests"
-      },
-      {
-        "test": "wtf_unittests"
-      }
-    ],
-    "scripts": [
-      {
-        "name": "webkit_lint",
-        "script": "webkit_lint.py"
-      },
-      {
-        "name": "webkit_python_tests",
-        "script": "webkit_python_tests.py"
-      }
-    ]
-  },
   "WebKit XP": {
     "gtest_tests": [
       {