Update existing SwiftShader jobs to use Vulkan instead of OpenGL

The SwiftShader OpenGL frontend is officially unsupported. They strictly
support their Vulkan frontend only.

Bug: skia:12218
Bug: skia:12820
Bug: skia:12826
Bug: skia:12829
Change-Id: Ib2e43783e18fcabfa2df9268c29bcd610350e5a2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/437149
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Christopher Dalton <csmartdalton@google.com>
8 files changed