Remove obsolete file chrome/renderer/resources/neterror.css.
Remove obsolete file chrome/renderer/resources/neterror.css.

This file was copied in https://codereview.chromium.org/1668963002
instead of being moved. The file in chrome/renderer/resources is
thus obsolete, removing it.

BUG=568486

Review URL: https://codereview.chromium.org/1702053002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#376486}

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