Update field trial test config for upcoming Finch experiment change.

Updates the OfflineContentOnDinoPage experiment group name and param
value to comply with the upcoming Finch experiment configuration change.

Bug: 852872
Change-Id: If110b3d215e9e6fd3184eaff6c33c9f3c5ac5ff7
Reviewed-on: https://chromium-review.googlesource.com/c/1292523Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Carlos Knippschild <carlosk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601370}

testing/variations/fieldtrial_testing_config.json

@@ -2952,9 +2952,9 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled",
+                    "name": "Enabled_List",
                     "params": {
-                        "ui-alternate": "content_preview"
+                        "ui-alternate": "content_list"
                     },
                     "enable_features": [
                         "NewNetErrorPageUI"