remove old code behind SK_SUPPORT_LEGACY_SETLENGTH

Bug: skia:
Change-Id: Ie47c9973e0981e8dd104fd6faf874d2ccf487093
Reviewed-on: https://skia-review.googlesource.com/c/193689
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>
3 files changed