Remove AutofillFieldMetadata entry from the testing config.

The study has ended, and there are notes in the server-side config and
in crbug.com/1111809 that this study is no longer needed.

Bug: 1126640, 1111809
Change-Id: I8806a5e6b2807cdd2644fe238a8f0df0597e7701
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626512Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#843502}

testing/variations/fieldtrial_testing_config.json

@@ -933,24 +933,6 @@
             ]
         }
     ],
-    "AutofillFieldMetadata": [
-        {
-            "platforms": [
-                "android",
-                "android_weblayer",
-                "chromeos",
-                "ios",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled"
-                }
-            ]
-        }
-    ],
     "AutofillKeyboardAccessory": [
         {
             "platforms": [