Remove unused target_visibility assignment from mojom gni

mojo/public/tools/bindings/mojom.gni

Index: mojo/public/tools/bindings/mojom.gni
diff --git a/mojo/public/tools/bindings/mojom.gni b/mojo/public/tools/bindings/mojom.gni
index 58b00c4db13994112a27eb4c3cca13c57321f271..51c28de250bac03220ad8683f95a0184300e791b 100644
--- a/mojo/public/tools/bindings/mojom.gni
+++ b/mojo/public/tools/bindings/mojom.gni
@@ -163,13 +163,6 @@ template("mojom") {
     }
   }
 
-  if (defined(invoker.visibility)) {
-    # Need to save this because the the target_name is overwritten inside the
-    # action to be that of the action itself. Only define this in the case the
-    # var is used to avoid unused var error.
-    target_visibility = [ ":$target_name" ]
-  }
-
   if (defined(invoker.sources)) {
     generator_target_name = target_name + "__generator"
     action_foreach(generator_target_name) {