Remove SyncE2ELatencyMeasurement from fieldtrial testing config

This feature was never meant for a full launch, and thus probably
shouldn't have been in the fieldtrial testing config in the first
place. It certainly makes no sense to enable it in browser tests and
developer builds.

Bug: 1009999
Change-Id: I3cf0eab118f8fff65cfe0f2ea99222fbe32344a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1936311
Auto-Submit: Marc Treib <treib@chromium.org>
Commit-Queue: Brian White <bcwhite@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719277}

testing/variations/fieldtrial_testing_config.json

@@ -6214,26 +6214,6 @@
             ]
         }
     ],
-    "SyncE2ELatency": [
-        {
-            "platforms": [
-                "android",
-                "windows",
-                "mac",
-                "chromeos",
-                "ios",
-                "linux"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "SyncE2ELatencyMeasurement"
-                    ]
-                }
-            ]
-        }
-    ],
     "SyncScryptCustomPassphrase": [
         {
             "platforms": [