Cleanup GrStrike management because we do not abandon strikes

Change-Id: I23e44ae389d00ae6dad6b04e24522f854dc98d75
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/267177
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
4 files changed