Fix visibility of //os:os

PiperOrigin-RevId: 253832479
Change-Id: I686ac0b6e2e74f37d4ff3361efd4bcd20d81d547

os/BUILD

diff --git a/os/BUILD b/os/BUILD
index 7c40476..5446917 100644
--- a/os/BUILD
+++ b/os/BUILD
@@ -11,10 +11,7 @@
 )
 
 # To add a new constraint_value see https://github.com/bazelbuild/platforms.
-constraint_setting(
-    name = "os",
-    visibility = ["//visibility:private"],
-)
+constraint_setting(name = "os")
 
 constraint_value(
     name = "osx",