Fix create_test_main deps flakiness

create_test_main.py script relies on cros_colors.generated.css, so add
it as a dep via webui_resources_grd to catch a broader range of
generated resources.

No-Tree-Checks: true
No-Try: true
Bug: 1145902
Change-Id: I7fb1681dd7f6db58ca74255eeb5be9ba10b1fa27
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2520483
Commit-Queue: Friedrich [CET] <fhorschig@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Auto-Submit: Joel Hockey <joelhockey@chromium.org>
Reviewed-by: dpapad <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824379}

ui/file_manager/file_manager/test/BUILD.gn

@@ -27,6 +27,7 @@ action("create_test_main") {
     "menu.js",
     "progress_center.js",
   ]
+  deps = [ "//ui/resources:webui_resources_grd" ]
   args = [ "--output=" + rebase_path(output, root_build_dir) ]
   outputs = [ output ]
 }