Extend expiry of flag enable-webrtc-new-encode-cpu-load-estimator

Bug: webrtc:8504,842613
Change-Id: I56f348087fdd5acb37c90cfe649d72890d985ba8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1857327Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Niels Möller <nisse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705507}

chrome/browser/flag-metadata.json

@@ -2008,7 +2008,7 @@
   {
     "name": "enable-webrtc-new-encode-cpu-load-estimator",
     "owners": [ "nisse" ],
-    "expiry_milestone": 77
+    "expiry_milestone": 85
   },
   {
     "name": "enable-webrtc-pipewire-capturer",