Remove HardwareMediaKeyHandling from the field trial testing config.

Bug: 1126640, 953480
Change-Id: I2ec62130c4fbe6d2160d8d3ee57e530111b0bce6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485515Reviewed-by: Tommy Steimel <steimel@chromium.org>
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#819018}

testing/variations/fieldtrial_testing_config.json

@@ -3187,22 +3187,6 @@
             ]
         }
     ],
-    "HardwareMediaKeyHandling": [
-        {
-            "platforms": [
-                "windows",
-                "mac"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "HardwareMediaKeyHandling"
-                    ]
-                }
-            ]
-        }
-    ],
     "HashedLoggingForHindsight": [
         {
             "platforms": [