Remove merge rules for //third_party/WebKit from M55 branch.

Less magic for merges.

BUG=563793
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/2404553002 .

Cr-Commit-Position: refs/branch-heads/2883@{#29}
Cr-Branched-From: 614d31daee2f61b0180df403a8ad43f20b9f6dd7-refs/heads/master@{#423768}
1 file changed