[variations] Remove config for enabled ParkableStringsToDisk feature.

Bug: 1029320
Change-Id: Ia58e3c4c381fe34922888fb5d7cbb4282ccafda3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2412293
Commit-Queue: Benoit L <lizeb@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807448}

testing/variations/fieldtrial_testing_config.json

@@ -5167,25 +5167,6 @@
             ]
         }
     ],
-    "ParkableStringsToDisk": [
-        {
-            "platforms": [
-                "android",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "ParkableStringsToDisk",
-                    "enable_features": [
-                        "ParkableStringsToDisk"
-                    ]
-                }
-            ]
-        }
-    ],
     "PartitionConnectionsByNetworkIsolationKey": [
         {
             "platforms": [