Remove IRGenerator::coerce.

This was replaced by Type::coerceExpression. This CL removes the last
two call sites to reference the old `coerce` method.

Change-Id: I636501a6eb6991463e1975ac38169dee058cdf6f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/451738
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
3 files changed