Remove field trial of WinOOPSelectFileDialog

This feature has already been removed from the code base.

Bug: 73098
Change-Id: Ic6b5fc5660000f75a5f8bb474af1e5ba760bc6fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1853948Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Patrick Monette <pmonette@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705258}

testing/variations/fieldtrial_testing_config.json

@@ -7195,21 +7195,6 @@
             ]
         }
     ],
-    "WinOOPSelectFileDialog": [
-        {
-            "platforms": [
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "WinOOPSelectFileDialog"
-                    ]
-                }
-            ]
-        }
-    ],
     "history-manipulation-intervention": [
         {
             "platforms": [