Recently the callstats runner started crashing due to scipy imports.

This CL moves the import to mitigate the crashes.

TBR=machenbach@chromium.org

Bug: v8:10269
Change-Id: I67c2093f12ae287354a59e9cd32b79c6288b8edd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2078571Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Auto-Submit: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66483}