Update fieldtrial config for DisableLatencyRecoveryDesktop

Originally, we were targeting disabling both impl thread and main thread
latency recoveries for DisableLatencyRecoveryDesktop experiment.
However, current Finch experiment results on canara/dev and beta show
that this config would likely have some regressions and the config with
the least regressions and the most improvements would probably be
EnabledImplDisabledMain, i.e. disabling latency recovery on main thread
only.

Bug: 993895,1060144,1060321,1060519,1060535,1062789
Change-Id: I47d3dc6de0e395ee1cd42f1993a51cdeebdf96c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2121465Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755263}

testing/variations/fieldtrial_testing_config.json

@@ -1967,9 +1967,11 @@
             ],
             "experiments": [
                 {
-                    "name": "DisabledImplDisabledMain",
+                    "name": "EnabledImplDisabledMain",
+                    "enable_features": [
+                        "ImplLatencyRecovery"
+                    ],
                     "disable_features": [
-                        "ImplLatencyRecovery",
                         "MainLatencyRecovery"
                     ]
                 }