Revert "Add MemoryAblation to field_trial_config"

This reverts commit 68d73438.

Reason for revert: 
Landed this with intent to revert. Got expected memory regression alerts for this experiment, but no other perf bugs filed.

Bug:815149


Original change's description:
> Add MemoryAblation to field_trial_config
> 
> Bug: 
> Change-Id: I9224213ed8c00e710f065dd0f24e2b20ec9332e6
> Reviewed-on: https://chromium-review.googlesource.com/775321
> Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
> Commit-Queue: Maria Khomenko <mariakhomenko@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#538587}

TBR=asvitkine@chromium.org,mariakhomenko@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Ic617234d0831cf14f81daacf1c6a1682c71fc777
Reviewed-on: https://chromium-review.googlesource.com/937783Reviewed-by: Maria Khomenko <mariakhomenko@chromium.org>
Commit-Queue: Maria Khomenko <mariakhomenko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539239}

testing/variations/fieldtrial_testing_config.json

@@ -1952,24 +1952,6 @@
             ]
         }
     ],
-    "MemoryAblation": [
-        {
-            "platforms": [
-                "android"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "params": {
-                        "Size": "1048570"
-                    },
-                    "enable_features": [
-                        "MemoryAblation"
-                    ]
-                }
-            ]
-        }
-    ],
     "MojoCdm": [
         {
             "platforms": [