Update test_flags visibility.

Change-Id: Ic18fea850d77fce90316c4b7118331c459a15685
Bug: None
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/323080
Auto-Submit: Jeremy Leconte <jleconte@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Jeremy Leconte <jleconte@google.com>
Cr-Commit-Position: refs/heads/main@{#40916}
diff --git a/test/BUILD.gn b/test/BUILD.gn
index 6f06718..e7eaa09 100644
--- a/test/BUILD.gn
+++ b/test/BUILD.gn
@@ -1236,7 +1236,6 @@
   }
 
   rtc_library("test_flags") {
-    visibility = [ "*" ]
     testonly = true
     sources = [
       "test_flags.cc",