fix: remove module_ctx.extension_metadata

In the current Bzlmod setup, all repositories generated by the `graalvm`
extension may or may not be used by users and whether they should be
can't be predicted based on the given tags: Users that want to generate
toolchains need the `<name>_toolchains` repo, users that rely on SDK
files need the `<name>` repo.

For now, remove the use of `module_ctx.extension_metadata` so that no
warning is shown when users register toolchains in `<name>_toolchains`.
In the future, we should improve the way toolchains are registered with
Bzlmod by automatically registering a toolchain configured via tags.

Signed-off-by: Fabian Meumertzheim <fabian@meumertzhe.im>

extensions.bzl

@@ -34,18 +34,6 @@ def _gvm_impl(mctx):
  setup_actions = selected.setup_actions,
  )
 
- _extension_meta = {}
- if not mctx.root_module_has_non_dev_dependency:
- _extension_meta["root_module_direct_dev_deps"] = [selected.name]
- _extension_meta["root_module_direct_deps"] = []
- else:
- _extension_meta["root_module_direct_deps"] = [selected.name]
- _extension_meta["root_module_direct_dev_deps"] = []
-
- return mctx.extension_metadata(
- **_extension_meta
- )
-
 _graalvm = tag_class(attrs = {
  "name": attr.string(mandatory = True),
  "version": attr.string(mandatory = True),