[Autofill] Extend flags for profile validation experiment

I was on a long leave and would need to take care of this
in the coming days. Meanwhile, extending the flags to avoid expiry.

Change-Id: I06449f52c74f8d8d32d1f57bd1b2f302bb2b50ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1866088
Commit-Queue: Dominic Battré <battre@chromium.org>
Reviewed-by: Dominic Battré <battre@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707354}

chrome/browser/flag-metadata.json

@@ -303,12 +303,12 @@
   {
     "name": "autofill-profile-client-validation",
     "owners": [ "parastoog" ],
-    "expiry_milestone": 77
+    "expiry_milestone": 79
   },
   {
     "name": "autofill-profile-server-validation",
     "owners": [ "parastoog" ],
-    "expiry_milestone": 77
+    "expiry_milestone": 79
   },
   {
     "name": "autofill-prune-suggestions",