OOR-CORS: Update fieldtrial_testing_config

Update the file to match actual parameters that was fixed
to distribute parameters correctly.

Bug: 1001450, 1056037
Change-Id: I387be6a82e3ecc96d0c7b4a1c4975f97dde717ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2082222
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Auto-Submit: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746163}

testing/variations/fieldtrial_testing_config.json

@@ -3691,6 +3691,7 @@
                         "extra-safelisted-request-headers-for-enterprise": "x-googapps-allowed-domains"
                     },
                     "enable_features": [
+                        "ExtraSafelistedRequestHeadersForOutOfBlinkCors",
                         "OutOfBlinkCors"
                     ]
                 }