Extend lifetime of omnibox-search-engine-logo flag

Change-Id: I4c02e2326922ff76fdbc3a4a9a4dcd053bcf0e8f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2158930Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Brandon Wylie <wylieb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#761109}

chrome/browser/flag-metadata.json

@@ -3182,7 +3182,7 @@
   {
     "name": "omnibox-search-engine-logo",
     "owners": [ "wylieb", "chrome-omnibox-team@google.com" ],
-    "expiry_milestone": 82
+    "expiry_milestone": 90
   },
   {
     "name": "omnibox-short-bookmark-suggestions",