refactor: simplify toolchain registration

examples/lang_toolchains/BUILD

diff --git a/examples/lang_toolchains/BUILD b/examples/lang_toolchains/BUILD
index 26990cc..ea56b75 100644
--- a/examples/lang_toolchains/BUILD
+++ b/examples/lang_toolchains/BUILD
@@ -6,6 +6,7 @@
     command_line = "--python_out=%s",
     progress_message = "Generating Python proto_library %{label}",
     runtime = "@pypi//protobuf",
+    toolchain_type = "@rules_python//python/proto:toolchain_type",
 )
 
 proto_lang_toolchain(
@@ -13,17 +14,5 @@
     command_line = "--java_out=%s",
     progress_message = "Generating Java proto_library %{label}",
     runtime = "@protobuf-java_3_25_3//jar",
-)
-
-# Adapters to the register_toolchains call, adding the toolchain_type to above
-toolchain(
-    name = "protoc_py_toolchain.registration",
-    toolchain = ":protoc_py_toolchain",
-    toolchain_type = "@rules_python//python/proto:toolchain_type",
-)
-
-toolchain(
-    name = "protoc_java_toolchain.registration",
-    toolchain = ":protoc_java_toolchain",
     toolchain_type = "@rules_java//java/proto:toolchain_type",
 )