crostini: Make a warning icon yellow.

Bug: chromium:1084374
Test: Manual, deploy and look for yellow colour.
Change-Id: I870d458dd7ca179cea0a6b5317fd1c04613fbcb5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2208330
Commit-Queue: David Munro <davidmunro@google.com>
Auto-Submit: David Munro <davidmunro@google.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#769960}

chrome/browser/resources/settings/chromeos/crostini_page/crostini_disk_resize_dialog.html

@@ -33,6 +33,10 @@
         display: inline-block;
       }
 
+      #warningIcon {
+        --iron-icon-fill-color: var(--google-yellow-500);
+      }
+
       #message {
         margin-inline-end: auto;
       }