flags: assign wallet-service-use-sandbox

This flag never expires since it is used by TE to validate Payments
features.

Bug: None
Change-Id: If0bfbfce132ef1f979c277c3e9ed6987598ba53d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1570921
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Jared Saul <jsaul@google.com>
Cr-Commit-Position: refs/heads/master@{#652201}

chrome/browser/flag-metadata.json

@@ -3065,8 +3065,10 @@
   },
   {
     "name": "wallet-service-use-sandbox",
-    // "owners": [ "your-team" ],
-    "expiry_milestone": 76
+    "owners": [ "jsaul@google.com", "jiahuiguo", "payments-autofill-team@google.com" ],
+    // This flag is used by testing teams to run Google Payments calls against
+    // the development server environment.
+    "expiry_milestone": -1
   },
   {
     "name": "web-contents-occlusion",

chrome/browser/flag-never-expire-list.json

@@ -61,5 +61,6 @@
   "ui-slow-animations",
   "update-menu-item-custom-summary",
   "use-angle",
-  "use-sync-sandbox"
+  "use-sync-sandbox",
+  "wallet-service-use-sandbox"
 ]