Remove fast/forms/associatedFormControls-leak-nodes.html.

It is a test for a Document leak by Document::m_associatedFormControls
[1]. However [2] removed m_associatedFormControls, and now the test isn't
helpful.

[1] https://chromium.googlesource.com/chromium/src/+/ca06c84dc478d4af2aa0b37026da6fa1a679d02e
[2] https://chromium.googlesource.com/chromium/src/+/c7e3c1f85c4691489409104d9ab53d30b52cd8d9

BUG=674194

Review-Url: https://codereview.chromium.org/2572383002
Cr-Commit-Position: refs/heads/master@{#438751}
2 files changed