Extend show-metered-toggle to M92

This feature was expected to launch in M-86, but due to unanticipated dependencies in update_engine was disabled until those dependencies can be addressed.

BUG=971704

Change-Id: I3312633ffaa1004aecb3043dfc5ed98bece5624f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2567031
Auto-Submit: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Azeem Arshad <azeemarshad@chromium.org>
Reviewed-by: Azeem Arshad <azeemarshad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832365}

chrome/browser/flag-metadata.json

@@ -4361,7 +4361,7 @@
   {
     "name": "show-metered-toggle",
     "owners": [ "stevenjb" ],
-    "expiry_milestone": 87
+    "expiry_milestone": 92
   },
   {
     "name": "show-overdraw-feedback",