[ios] Fix typo: include header instead of mm file.

This caused a link error, duplicate symbols, in a jumbo build
experiment. How it ever worked in normal builds we'll never know.

Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I4136a153aa989f2187d745f291658ac4e05fa6db
Reviewed-on: https://chromium-review.googlesource.com/1244461
Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#594357}
1 file changed