Remove dependencies on old `iree-tools-xla` package

[Scott Todd]

There are references to iree-tools-xla, which was merged into iree-tools-tf along with adoption of StableHLO (see iree-org/iree#13068).

iree-jax/setup.py

Lines 53 to 60 in 584b6c1

 extras_require={ 
   "xla": [ 
     get_pinned_package("iree-tools-xla"), 
   ], 
   "test": [ 
     "lit", 
   ] 
 }, 

iree-jax/iree/jax/frontend.py

Lines 61 to 63 in 584b6c1

 return iree.compiler.tools.xla.compile_str(hlo_proto, 
                                            input_type=iree.compiler.InputType.XLA, 
                                            **options) 

Removing those might just be a matter of switching to newer packages / APIs, or other code changes might be needed.