Update SkParticleEffect comments based on review feedback

Change-Id: I3436ee95c4cc13067b53b170515fd10c19b329b3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/242136
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
1 file changed