Fix //net/spdy/OWNERS.

This file has a reference to a non-existing OWNERS file, causing
presubmits error on CLs touching this directory.

NOPRESUBMIT=true

Change-Id: If1a18e878db6de1e1f8eebdaccf5425796399fe3
Reviewed-on: https://chromium-review.googlesource.com/1017321Reviewed-by: Ryan Hamilton <rch@chromium.org>
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551851}

net/spdy/OWNERS

-file://net/http2/OWNERS
+file://net/third_party/http2/OWNERS
 
 # COMPONENT: Internals>Network>HTTP2