Remove Net.SSLSecureRenegotiation histogram

The histogram has expired and I don't currently have the cycles to chase
this one down. (On the client, the correct mitigation is to reject *all*
connections without renegotiation info, so this would only have been a
half-measure anyway.)

Bug: 975173
Change-Id: Ib64f4796abe057cf5df606c56926e45682d8cecc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1727093
Commit-Queue: David Benjamin <davidben@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Steven Valdez <svaldez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683429}
3 files changed