Suppress MSVC C4756 (constant arithmetic overflow) in fiddle examples

Bug: skia:
Change-Id: I5611ac4b91baf67c0d895167b3da4ef69a8972bb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/201690
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>