Revert "Enable sandboxing for audio service field trial testing on Windows and Mac."

This reverts commit 5fddb84e.

Reason for revert: Speculative revert for failing WebRTC browser tests.

Original change's description:
> Enable sandboxing for audio service field trial testing on Windows and Mac.
> 
> Bug: 832666
> Change-Id: Ic64a983498156bba73c458f2abc872db337d1999
> Reviewed-on: https://chromium-review.googlesource.com/1216142
> Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
> Commit-Queue: Marina Ciocea <marinaciocea@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#589911}

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

Change-Id: Ib0a488a759dea9176b6096bdfafd710f6c3aa8bc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 832666, 882780
Reviewed-on: https://chromium-review.googlesource.com/1218942Reviewed-by: Max Morin <maxmorin@chromium.org>
Commit-Queue: Max Morin <maxmorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590233}

testing/variations/fieldtrial_testing_config.json

@@ -461,31 +461,13 @@
     "AudioService": [
         {
             "platforms": [
+                "linux",
                 "mac",
                 "windows"
             ],
             "experiments": [
                 {
-                    "name": "AudioProcess_LaunchOnStartup_Sandboxed_v7",
-                    "params": {
-                        "teardown_timeout_s": "0"
-                    },
-                    "enable_features": [
-                        "AudioServiceAudioStreams",
-                        "AudioServiceLaunchOnStartup",
-                        "AudioServiceOutOfProcess",
-                        "AudioServiceSandbox"
-                    ]
-                }
-            ]
-        },
-        {
-            "platforms": [
-                "linux"
-            ],
-            "experiments": [
-                {
-                    "name": "AudioProcess_LaunchOnStartup_v7",
+                    "name": "AudioProcess_LaunchOnStartup_v6",
                     "params": {
                         "teardown_timeout_s": "0"
                     },