[Safety Tips] Bump expiry of safety tips flag.

Change-Id: I2200d62068bde5defc3ce0ae65978b6850d7520d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2090363
Commit-Queue: Joe DeBlasio <jdeblasio@chromium.org>
Commit-Queue: Mustafa Emre Acer <meacer@chromium.org>
Auto-Submit: Joe DeBlasio <jdeblasio@chromium.org>
Reviewed-by: Mustafa Emre Acer <meacer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747791}

chrome/browser/flag-metadata.json

@@ -3172,7 +3172,7 @@
   {
     "name": "safety-tips",
     "owners": [ "jdeblasio", "estark", "meacer" ],
-    "expiry_milestone": 82
+    "expiry_milestone": 84
   },
   {
     "name": "same-site-by-default-cookies",