Update the finch feature name to the correct value.

Change-Id: Iab69731e7c7f13d792b64b0caf7e253417fb756c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2097994
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Auto-Submit: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749268}

testing/variations/fieldtrial_testing_config.json

@@ -1010,7 +1010,7 @@
                         "rely_on_android_network_detection": "true"
                     },
                     "enable_features": [
-                        "RelyOnAndroidNetworkDetection"
+                        "BackgroundSync"
                     ]
                 }
             ]