[bzl] Remove obsolete `output_to_genfiles = True` (#83944)

The [bazel docs](https://bazel.build/rules/lib/globals/bzl#rule)
discourage setting this. The comments about being necessary for headers
or genrules seem to be obsolete, at least for the LLVM tree itself.

The effect of this is that generated files will go to `bazel-bin`
instead of `bazel-genfiles`.

One external use was fixed here:
https://github.com/google/jax/commit/32bb3b06132b4256cd8674fb98bce057dc968610.