[Autorollers] Increase skia->flutter cores for license script
[Autorollers] Increase skia->flutter cores for license script

This is an experiment to see how long license scripts take with more
cores.

Change-Id: I1cef698ca99d01df07c9ebdd97feb18687909f93
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/280337
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot