Remove a stray semicolon from websocket_messages.h.
Remove a stray semicolon from websocket_messages.h.

TBR=inferno@chromium.org,ricea@chromium.org
BUG=585138
NOTRY=true

Review URL: https://codereview.chromium.org/1680753002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#374173}

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