Fix broken reference to `@go_sdk` in tests

MODULE.bazel

diff --git a/MODULE.bazel b/MODULE.bazel
index 1c3c4d1..cae13fb 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -55,3 +55,11 @@
 
 bazel_dep(name = "bazel_skylib_gazelle_plugin", version = "1.4.1", dev_dependency = True)
 bazel_dep(name = "stardoc", version = "0.5.1", dev_dependency = True, repo_name = "io_bazel_stardoc")
+
+go_sdk_dev = use_extension("@io_bazel_rules_go//go:extensions.bzl", "go_sdk", dev_dependency = True)
+
+# Known to exist since it is instantiated by rules_go itself.
+use_repo(
+    go_sdk_dev,
+    go_sdk = "go_default_sdk",
+)