Extending language detection flag expiry to M84.

R=aboxhall, dmazzoni

Change-Id: Ibbd5f6b9e8ad6ec954265b9c7eeb5b798055530b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2066486
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745185}

chrome/browser/flag-metadata.json

@@ -1274,12 +1274,12 @@
   {
     "name": "enable-experimental-accessibility-language-detection",
     "owners": [ "chrishall", "//ui/accessibility/OWNERS" ],
-    "expiry_milestone": 82
+    "expiry_milestone": 84
   },
   {
     "name": "enable-experimental-accessibility-language-detection-dynamic",
     "owners": [ "chrishall", "//ui/accessibility/OWNERS" ],
-    "expiry_milestone": 83
+    "expiry_milestone": 84
   },
   {
     "name": "enable-experimental-accessibility-switch-access",