Remove deprecated merge image filter header Bug: skia:11230 Change-Id: I50a9fb86a9054b96b3088b06f625dea418f53db8 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/371962 Commit-Queue: Michael Ludwig <michaelludwig@google.com> Reviewed-by: Robert Phillips <robertphillips@google.com>