Adjust visibility of heterogeneous_lookup_testing.h

PiperOrigin-RevId: 846842509
Change-Id: I91a82eb9bafd01b3341efcd9aef3b699dc8fe10a
diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index f24bad7..15fb0a5 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -1234,6 +1234,9 @@
     hdrs = ["internal/heterogeneous_lookup_testing.h"],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+        "//absl/container:__pkg__",
+    ],
     deps = [
         "//absl/base:config",
         "//absl/container:test_instance_tracker",