Remove TokenBinding fieldtrial config

The token binding feature was removed in crrev.com/584532 (M70) - this
is overdue for being removed.

Bug: 875046
Change-Id: I121028692ba02602c54077401dc15eb176c8e67b
Reviewed-on: https://chromium-review.googlesource.com/c/1351712Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Nick Harper <nharper@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611827}

testing/variations/fieldtrial_testing_config.json

@@ -4751,25 +4751,6 @@
             ]
         }
     ],
-    "TokenBinding": [
-        {
-            "platforms": [
-                "android",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "TokenBinding",
-                    "enable_features": [
-                        "token-binding"
-                    ]
-                }
-            ]
-        }
-    ],
     "TranslateCompactUI": [
         {
             "platforms": [