Fix an off-by-one in the max index passed to glDrawRangeElements by DrawMeshOp

See https://github.com/flutter/flutter/issues/115919

Change-Id: Ibf9c900810ce1e9a8806eff4014bac162621139a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/631396
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
1 file changed