OOR-CORS: Remove fieldtrial_testing_config for relaunch

Since the launch plan was changed, it's better not to have
an entry in the fieldtrial_testing_config.

We turned down the feature on all platforms, except for cast,
and will relaunch it at m79 with enterprise friendly mitigation.

We continue to run affected tests at dedicated oor-cors fyi bots.

Bug: 905971
Change-Id: I9270b149ce5bd4131c485c29a81cb1a2a4221c95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1800137
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699303}

testing/variations/fieldtrial_testing_config.json

@@ -4053,27 +4053,6 @@
             ]
         }
     ],
-    "OutOfBlinkCors": [
-        {
-            "platforms": [
-                "android",
-                "android_webview",
-                "chromeos",
-                "ios",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "OutOfBlinkCors"
-                    ]
-                }
-            ]
-        }
-    ],
     "OutOfProcessQuarantine": [
         {
             "platforms": [