Remove "experimental" comments regarding RG_F16 and RGBA_16161616

These two formats are now exercised in the wacky_yuv_formats GM

Change-Id: I07a5649401b7928e8c4666e39793915ac1d45646
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/242560
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
13 files changed