Add WebRTC-Bwe-MaxRttLimit to Field Trial testing config.

Change-Id: Ib715fb23b3fcb21997215e2c5d973f10e3cee92b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1631589Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Nikita Zetilov <zetilovn@google.com>
Cr-Commit-Position: refs/heads/master@{#667136}

testing/variations/fieldtrial_testing_config.json

@@ -6182,6 +6182,24 @@
             ]
         }
     ],
+    "WebRTC-Bwe-MaxRttLimit": [
+        {
+            "platforms": [
+                "windows",
+                "mac",
+                "chromeos",
+                "linux",
+                "ios",
+                "android",
+                "android_webview"
+            ],
+            "experiments": [
+                {
+                    "name": "persist,limit:3s,fraction:.8,interval:1s"
+                }
+            ]
+        }
+    ],
     "WebRTC-BweAllocProbingOnlyInAlr": [
         {
             "platforms": [