[rules score]: adapt visibility

Co-authored-by: SebSparrowHawk 211667837+SebSparrowHawk@users.noreply.github.com

Author: hoe-jo

bazel/rules/rules_score/BUILD

@@ -154,7 +154,10 @@ sphinx_toolchain(
     sphinx = ":score_build",
 )
 
-toolchain_type(name = "toolchain_type")
+toolchain_type(
+    name = "toolchain_type",
+    visibility = ["//visibility:public"],
+)
 
 toolchain(
     name = "sphinx_default_toolchain",