Remove _apple_toolchain field from apple_package() rule

Summary:
Removes the `_apple_toolchain` field from `apple_package()` because it's not used anymore. The toolchain is used via the `apple_ipa_package()` "private" rule now.

This means that `apple_package()` execution platform is no longer constrained by the exec platform for the host-based toolchain used for `.ipa` creation.

Differential Revision: D61264638

fbshipit-source-id: 5c3db0741b4f247a826934daec426370c7ca555a

apple/apple_rules_impl.bzl

@@ -36,7 +36,6 @@ load(
     "apple_dsymutil_attrs",
     "apple_test_extra_attrs",
     "apple_xcuitest_extra_attrs",
-    "get_apple_bundle_toolchain_attr",
     "get_apple_toolchain_attr",
     "get_apple_xctoolchain_attr",
     "get_apple_xctoolchain_bundle_id_attr",
@@ -151,7 +150,6 @@ extra_attributes = {
             ),
             default = [],
         ),
-        "_apple_toolchain": get_apple_bundle_toolchain_attr(),
         "_apple_tools": attrs.exec_dep(default = "prelude//apple/tools:apple-tools", providers = [AppleToolsInfo]),
         "_ipa_compression_level": attrs.enum(IpaCompressionLevel.values()),
         "_ipa_package": attrs.dep(),