[mlir][GPU] Remove the SerializeToCubin pass (#82486)

The `SerializeToCubin` pass was deprecated in September 2023 in favor of
GPU compilation attributes; see the [GPU
compilation](https://mlir.llvm.org/docs/Dialects/GPU/#gpu-compilation)
section in the `gpu` dialect MLIR docs.
This patch removes `SerializeToCubin` from the repo.