Revert "Changing AudioService experiment field trial to test service launch on startup"

This reverts commit ec3716fd.

Reason for revert: It broke WebRTC performance tests which capture system audio loopback. The reason is unclear, but looks like tests-specific: audio works with manual testing; and the test only changed event timing at the process startup.
Reverting for now to have WebRTC audio quality test coverage.

Bug:850936

Original change's description:
> Changing AudioService experiment field trial to test service launch on startup
> 
> [1] introduced AudioServiceLaunchOnStartup feature which we want to roll out
> with a new experiment group. Updating field trial to run the config on bots
> first.
> 
> [1] https://chromium-review.googlesource.com/c/chromium/src/+/1104681
> 
> Bug: 851611,853781
> Change-Id: I3796a8ac205a6d37706a86e8647c933ee510f41a
> Reviewed-on: https://chromium-review.googlesource.com/1105957
> Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
> Commit-Queue: Olga Sharonova <olka@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#568485}

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

Change-Id: Ic50b37d434bc75fca78585ead8c964815bcd2cf0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 851611, 853781
Reviewed-on: https://chromium-review.googlesource.com/1107957Reviewed-by: Olga Sharonova <olka@chromium.org>
Commit-Queue: Olga Sharonova <olka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568822}

testing/variations/fieldtrial_testing_config.json

@@ -359,13 +359,12 @@
             ],
             "experiments": [
                 {
-                    "name": "AudioProcess_LaunchOnStartup_v2",
+                    "name": "AudioProcess",
                     "params": {
-                        "teardown_timeout_s": "0"
+                        "teardown_timeout_s": "300"
                     },
                     "enable_features": [
                         "AudioServiceAudioStreams",
-                        "AudioServiceLaunchOnStartup",
                         "AudioServiceOutOfProcess"
                     ]
                 }