remove exir:_warnings dep from executorch_pybindings buck rule (pytorch#8710)

Per @larryliu0820. It was blocking buck2 build //runtime/... (which is still failing, but differently)

Author: swolchok

shim_et/xplat/executorch/extension/pybindings/pybindings.bzl

@@ -52,7 +52,6 @@ def executorch_pybindings(python_module_name, srcs = [], cppdeps = [], visibilit
             "-DEXECUTORCH_PYTHON_MODULE_NAME={}".format(python_module_name),
         ],
         deps = [
-            "//executorch/exir:_warnings",
             "//executorch/runtime/core:core",
         ] + cppdeps,
         external_deps = [