Revert "Enable AudioServiceSandbox flag in audio service field trial testing."

This reverts commit 6caca443.

Reason for revert: I suspect that this CL is causing https://crbug.com/890850

Original change's description:
> Enable AudioServiceSandbox flag in audio service field trial testing.
> 
> Bug: 832666
> Change-Id: I3ec5dbea8e34f3a9295723def845e49b2bb59af3
> Reviewed-on: https://chromium-review.googlesource.com/1240280
> Reviewed-by: Steven Holte <holte@chromium.org>
> Commit-Queue: Marina Ciocea <marinaciocea@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#595397}

TBR=holte@chromium.org,marinaciocea@chromium.org

Change-Id: I5e6d1a9e153003c086ce8c2f247230d4832ce99b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 832666, 890850
Reviewed-on: https://chromium-review.googlesource.com/1254746Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595464}

testing/variations/fieldtrial_testing_config.json

@@ -520,15 +520,14 @@
             ],
             "experiments": [
                 {
-                    "name": "AudioProcess_LaunchOnStartup_Sandboxed_v7",
+                    "name": "AudioProcess_LaunchOnStartup_v6",
                     "params": {
                         "teardown_timeout_s": "0"
                     },
                     "enable_features": [
                         "AudioServiceAudioStreams",
                         "AudioServiceLaunchOnStartup",
-                        "AudioServiceOutOfProcess",
-                        "AudioServiceSandbox"
+                        "AudioServiceOutOfProcess"
                     ]
                 }
             ]