Rename the ExperimentalHardwareEchoCancellation origin trial

Renaming it to ExperimentalHardwareEchoCancellation2, so that new
tokens don't trigger the old behaviour in older versions of Chrome.

The runtime flag retains its name, since that's user controlled.

Bug: 854577, 846270
Change-Id: I577e37082ed4cd84d4e77dc6f13155a4eba49131
Reviewed-on: https://chromium-review.googlesource.com/1106338Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Oskar Sundbom <ossu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568821}

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -430,7 +430,7 @@
     },
     {
       name: "ExperimentalHardwareEchoCancellation",
-      origin_trial_feature_name: "ExperimentalHardwareEchoCancellation",
+      origin_trial_feature_name: "ExperimentalHardwareEchoCancellation2",
       status: "experimental",
     },
     // Enables a set of features intended to help improve web developer