Retract some headers (mainly GrOpsTask.h)

Bug: skia:11837
Change-Id: I22691e282fe9e994aafe32bed97f284d54595f74
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/432936
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
5 files changed