Change ThirdPartyOriginTrial to stable

Launch approval in crbug.com/1077038.

Bug: 1069623
Change-Id: I2c739c82aecfcefbb76a9fe9a142362412bde8bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391724Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Jason Chase <chasej@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804012}

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1842,7 +1842,7 @@
     },
     {
       name: "ThirdPartyOriginTrials",
-      status: "test",
+      status: "stable",
     },
     {
       name: "TimerThrottlingForBackgroundTabs",