[WPT Sync] Unskip wpt/lint.whitelist in W3CImportExpectations

This step is in preparation for running the WPT linter as part of
Chromium PRESUBMIT. Lint errors make up the majority of cases when
and upstream WPT PR fails Travis CI, so running the same lint
check in PRESUBMIT will help curb a large number of stuck PRs.

Bug: 686927
Change-Id: Ic54d73368db2bcc0a5ea09411c674681bbaa6972
Reviewed-on: https://chromium-review.googlesource.com/471787
Commit-Queue: Jeff Carpenter <jeffcarp@chromium.org>
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#463007}

third_party/WebKit/LayoutTests/W3CImportExpectations

@@ -289,7 +289,6 @@ external/wpt/imagebitmap-renderingcontext [ Skip ]
 # external/wpt/innerText [ Pass ]
 external/wpt/js [ Skip ]
 external/wpt/lint [ Skip ]
-external/wpt/lint.whitelist [ Skip ]
 external/wpt/manifest [ Skip ]
 external/wpt/mathml [ Skip ]
 ## Owners: none; No tests in the directory.