Remove FlexNG entry from the testing config.

Bug: 1126640
Change-Id: I81efe729e921c24db6662daa2c1f87f4d36c73c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626515Reviewed-by: David Grogan <dgrogan@chromium.org>
Commit-Queue: David Grogan <dgrogan@chromium.org>
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#843246}

testing/variations/fieldtrial_testing_config.json

@@ -3226,26 +3226,6 @@
             ]
         }
     ],
-    "FlexNG": [
-        {
-            "platforms": [
-                "android",
-                "android_webview",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled_20200406",
-                    "enable_features": [
-                        "FlexNG"
-                    ]
-                }
-            ]
-        }
-    ],
     "FormControlsDarkMode": [
         {
             "platforms": [