chore: cleanup unused attributes for the host_toolchain repo rule (#2195)

The attributes were not used, so we can remove them for now.

Author: aignas

examples/bzlmod/MODULE.bazel.lock

@@ -692,12 +692,7 @@ def python_register_toolchains(
                 platform = platform,
             ))
 
-    host_toolchain(
-        name = name + "_host",
-        python_version = python_version,
-        user_repository_name = name,
-        platforms = loaded_platforms,
-    )
+    host_toolchain(name = name + "_host")
 
     toolchain_aliases(
         name = name,

python/private/python_repositories.bzl

@@ -314,14 +314,6 @@ toolchain_aliases repo because referencing the `python` interpreter target from
 this repo causes an eager fetch of the toolchain for the host platform.
     """,
     attrs = {
-        "platforms": attr.string_list(
-            doc = "List of platforms for which aliases shall be created",
-        ),
-        "python_version": attr.string(doc = "The Python version."),
-        "user_repository_name": attr.string(
-            mandatory = True,
-            doc = "The base name for all created repositories, like 'python38'.",
-        ),
         "_rule_name": attr.string(default = "host_toolchain"),
         "_rules_python_workspace": attr.label(default = Label("//:WORKSPACE")),
     },