Fix gn get_label_info comment

tools/gn/function_get_label_info.cc

Index: tools/gn/function_get_label_info.cc
diff --git a/tools/gn/function_get_label_info.cc b/tools/gn/function_get_label_info.cc
index 267c7b0f0ab56a08766f5bd1dd9549128a705805..a67a3719921d2b88cef35ece1338319393bc4d89 100644
--- a/tools/gn/function_get_label_info.cc
+++ b/tools/gn/function_get_label_info.cc
@@ -71,7 +71,7 @@ Examples
   get_label_info(":foo", "name")
   # Returns string "foo".
 
-  get_label_info("//foo/bar:baz", "gen_dir")
+  get_label_info("//foo/bar:baz", "target_gen_dir")
   # Returns string "//out/Debug/gen/foo/bar".
 )*";