Skip LayoutTests/external/wpt/resources/test for wpt import

We're not actually running these tests, so like
external/wpt/resources/webidl2/test there's not much reason to import
them, and the risk of confusion if we do.

Unskip README.md as it's harmless or potentially useful, however.

This will take effect at the next import.

No-Try: true
Change-Id: I92a693417736fa605feedd88d33d094ead3e515c
Reviewed-on: https://chromium-review.googlesource.com/786032
Commit-Queue: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518797}

third_party/WebKit/LayoutTests/W3CImportExpectations

@@ -148,7 +148,7 @@ external/wpt/js [ Skip ]
 external/wpt/mathml [ Skip ]
 external/wpt/old-tests [ Skip ]
 external/wpt/proximity [ Skip ]
-external/wpt/resources/webidl2/README.md [ Skip ]
+external/wpt/resources/test [ Skip ]
 external/wpt/resources/webidl2/test [ Skip ]
 external/wpt/serve.py [ Skip ]
 external/wpt/server-side.md [ Skip ]