Replace Label(...).workspace_name with explicit repo name

With the repository mappings used by bzlmod, the
Label(...).workspace_name construct always returns the canonical,
post-repo mapping repo name, which can't be used to construct a valid
label. Until bazelbuild/bazel#15593 has been
fixed, we have to hardcode the non-canonical repo name here.

go/private/sdk.bzl

@@ -233,7 +233,7 @@ def _sdk_build_file(ctx, platform):
             "{goos}": goos,
             "{goarch}": goarch,
             "{exe}": ".exe" if goos == "windows" else "",
-            "{rules_go_repo_name}": Label("//go/private:BUILD.sdk.bazel").workspace_name,
+            "{rules_go_repo_name}": "io_bazel_rules_go",
         },
     )