Update expiration dates of tab hover card and tab hover card images flags.

Bug: 910739, 1152816
Change-Id: I44aa8b946783511e3e61c2b59625b338882dad8f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2568538Reviewed-by: Dana Fried <dfried@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Auto-Submit: Caroline Rising <corising@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834482}

chrome/browser/flag-metadata.json

@@ -4596,12 +4596,12 @@
   {
     "name": "tab-hover-card-images",
     "owners": [ "dfried", "corising", "//chrome/browser/ui/views/tabs/OWNERS" ],
-    "expiry_milestone": 88
+    "expiry_milestone": 90
   },
   {
     "name": "tab-hover-cards",
     "owners": [ "corising", "//chrome/browser/ui/views/tabs/OWNERS" ],
-    "expiry_milestone": 88
+    "expiry_milestone": 90
   },
   {
     "name": "tab-outlines-in-low-contrast-themes",