Fix gn get_label_info comment

Review-Url: https://codereview.chromium.org/2929893002
Cr-Original-Commit-Position: refs/heads/master@{#478042}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f8bf5083fb27aa1b7c5786854f62da9b5b5532f3

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 267c7b0..a67a371 100644
--- a/tools/gn/function_get_label_info.cc
+++ b/tools/gn/function_get_label_info.cc
@@ -71,7 +71,7 @@
   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".
 )*";