Extend some flags that we still intend to use.

Change-Id: Id7f2bcd69b2343b9bb9b40ad037f7e570aaa71e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1783481Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Peter Williamson <petewil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693799}

chrome/browser/flag-metadata.json

@@ -2511,12 +2511,12 @@
   {
     "name": "offline-pages-live-page-sharing",
     "owners": [ "petewil", "jianli", "offline-dev" ],
-    "expiry_milestone": 76
+    "expiry_milestone": 86
   },
   {
     "name": "offline-pages-load-signal-collecting",
     "owners": [ "petewil", "offline-dev" ],
-    "expiry_milestone": 76
+    "expiry_milestone": 86
   },
   {
     "name": "offline-pages-pending-download",
@@ -2531,12 +2531,12 @@
   {
     "name": "offline-pages-renovations",
     "owners": [ "petewil", "offline-dev" ],
-    "expiry_milestone": 76
+    "expiry_milestone": 86
   },
   {
     "name": "offline-pages-resource-based-snapshot",
     "owners": [ "petewil", "offline-dev" ],
-    "expiry_milestone": 76
+    "expiry_milestone": 86
   },
   {
     "name": "offlining-recent-pages",