move #include out of header

Not important, just puzzled me when reading it.
A little IWYU.

Change-Id: I3199e6a4c34794f07bddda31032dfa871ce9bc4f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/294021
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed