Remove excess spaces and reformat comment in spdy_session_pool.h.

This is a follow-up to https://crrev.com/c/1570914.

Bug: 912727
Change-Id: I284dbb580bb396da787c7d2f5755428458f88aeb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577479
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Bence Béky <bnc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652866}
1 file changed