Remove unnecessary SkImageFilters.cpp

After having moved all other filter factory definitions into their
per-filter implementation files, all that remained was the
MatrixTransform factory, which is just moved into the
SkMatrixImageFilter CPP file.

Bug: skia:11230
Change-Id: Ifd7f3eb58ef1d05ed6d0aef0517ca9caa01436d8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/372121
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
4 files changed