Disable window_manager_apptests again...

I fixed local crashes in https://codereview.chromium.org/1107133002
The bot fails on gl_surface init, which I can't repro:
  http://build.chromium.org/p/chromium.mojo/builders/Chromium%20Mojo%20Linux/builds/4898/steps/app_tests/logs/stdio

[0427/144427:ERROR:gl_surface_x11.cc(98)] XOpenDisplay failed.
[0427/144427:ERROR:gl_surface_x11.cc(62)] NativeViewGLSurfaceOSMesa::InitializeOneOff failed.
[0427/144427:FATAL:gl_surface.cc(136)] Check failed: InitializeOneOffImplementation( impl, fallback_to_osmesa, gpu_service_logging, disable_gl_drawing).

BUG=480040
TEST=Bot goes green again.
TBR=sky@chromium.org

Review URL: https://codereview.chromium.org/1106363002

Cr-Commit-Position: refs/heads/master@{#327159}

mojo/tools/data/apptests

@@ -44,8 +44,9 @@ tests = [
     "type": "gtest_isolated",
     "shell-args": ["--url-mappings=mojo:window_manager=mojo:test_window_manager"]
   },
-  {
-    "test": "mojo:window_manager_apptests",
-    "shell-args": ["--use-test-config", "--use-headless-config"]
-  },
+  # TODO(msw): Fix and enable window_manager_apptests: http://crbug.com/480040
+  #{
+  #  "test": "mojo:window_manager_apptests",
+  #  "shell-args": ["--use-test-config", "--use-headless-config"]
+  #},
 ]