Use more explicit visibilities.

RELNOTES: None.
PiperOrigin-RevId: 229371245

lib/BUILD

diff --git a/lib/BUILD b/lib/BUILD
index ce8483b..a1630b9 100644
--- a/lib/BUILD
+++ b/lib/BUILD
@@ -1,10 +1,9 @@
 licenses(["notice"])
 
-package(default_visibility = ["//visibility:public"])
-
 # Consumed by bazel tests.
 filegroup(
     name = "for_bazel_tests",
     testonly = 1,
     srcs = glob(["**"]),
+    visibility = ["//:__pkg__"],
 )