Fix version in builder name for chromium.webkit Mac retina recipe config.

testing/buildbot/chromium.webkit.json

 {
   "Linux ChromiumOS Tests (1)": {
     "gtest_tests": [
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "accessibility_unittests"
       },
       {
@@ skipping 835 matching lines @@
       {
         "name": "webkit_lint",
         "script": "webkit_lint.py"
       },
       {
         "name": "webkit_python_tests",
         "script": "webkit_python_tests.py"
       }
     ]
   },
-  "WebKit Mac10.8 (retina)": {
+  "WebKit Mac10.9": {
     "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 Mac10.9": {
+  "WebKit Mac10.9 (retina)": {
     "gtest_tests": [
       {
         "test": "blink_heap_unittests"
       },
       {
         "test": "blink_platform_unittests"
       },
       {
         "test": "webkit_unit_tests"
       },
@@ skipping 136 matching lines @@
         "name": "webkit_lint",
         "script": "webkit_lint.py"
       },
       {
         "name": "webkit_python_tests",
         "script": "webkit_python_tests.py"
       }
     ]
   }
 }