Cleaning up unused code

Bug: b/153177839
Change-Id: I42479778f0f6ec9a955ba7f863766429b68c73a3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/43468
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>