Remove FragmentItem from the testing config.

Bug: 1126640, 1154531
Change-Id: I132a47d6962bc2479b1096a409b2602e841a6a6f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626520
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843522}

testing/variations/fieldtrial_testing_config.json

@@ -3197,26 +3197,6 @@
             ]
         }
     ],
-    "FragmentItem": [
-        {
-            "platforms": [
-                "android",
-                "android_webview",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled_20200615",
-                    "enable_features": [
-                        "FragmentItem"
-                    ]
-                }
-            ]
-        }
-    ],
     "FreezeBackgroundTabOnNetworkIdle": [
         {
             "platforms": [