[examples] Mark driver_example_mod_tests as flaky.

This test is both flaky and uses an outdated method of running
Dart/Flutter tests.  It is likely exposing real issues so we mark
it as flaky instead of deleting it.

Bug: 38260
Change-Id: Ie7eec5b4691781fa4dd523fa5969771af637c4fa
diff --git a/examples/test/driver_example_mod/BUILD.gn b/examples/test/driver_example_mod/BUILD.gn
index 73a7750..e14ac06 100644
--- a/examples/test/driver_example_mod/BUILD.gn
+++ b/examples/test/driver_example_mod/BUILD.gn
@@ -64,8 +64,18 @@
   # release CI/CQ.
   if (is_debug) {
     environments += [
-      nuc_env,
-      vim2_env,
+      {
+        dimensions = {
+          device_type = "Intel NUC Kit NUC7i5DNHE"
+        }
+        tags = [ "flaky" ]  # fxb/38260
+      },
+      {
+        dimensions = {
+          device_type = "Khadas Vim2 Max"
+        }
+        tags = [ "flaky" ]  # fxb/38260
+      },
     ]
   }
 }