remove legacy utils for camera3d

Change-Id: I43845925aa7f3bf880b4a63fe09d9d69e7574ad5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/290376
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
2 files changed