remove (unused) clipmask from savelayer

Change-Id: I44f64a8c98c019a8f4878b0b6f6d82489aa8252c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/296179
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Mike Reed <reed@google.com>
20 files changed