Extend crostini-gpu-support and crostini-usb-allow-unsupported flags.

Bug: None
Change-Id: I3b7a78025ea186768f4f9f81bb40df8c341f70fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1916530
Auto-Submit: Nicholas Verne <nverne@chromium.org>
Reviewed-by: Nic Hollingum <hollingum@google.com>
Commit-Queue: Nic Hollingum <hollingum@google.com>
Cr-Commit-Position: refs/heads/master@{#715525}

chrome/browser/flag-metadata.json

@@ -577,12 +577,12 @@
   {
     "name": "crostini-gpu-support",
     "owners": [ "nverne", "benwells" ],
-    "expiry_milestone": 78
+    "expiry_milestone": 85
   },
   {
     "name": "crostini-usb-allow-unsupported",
     "owners": [ "nverne", "benwells" ],
-    "expiry_milestone": 77
+    "expiry_milestone": 85
   },
   {
     "name": "crostini-usb-support",