Update name of DisableFirstRunAutoImport default experiment to match finch config

TBR=rkaplow@chromium.org
BUG=555550

Review-Url: https://codereview.chromium.org/2610853008
Cr-Commit-Position: refs/heads/master@{#441692}

testing/variations/fieldtrial_testing_config.json

@@ -483,7 +483,7 @@
             ],
             "experiments": [
                 {
-                    "name": "DisableFirstRunAutoImport",
+                    "name": "AutoImportDisabled",
                     "enable_features": [
                         "DisableFirstRunAutoImport"
                     ]