readdir is safer than readdir_r.

The upstream cpplint.py already made this change.

Change-Id: I9614d51080557eab6730cffd476e01e7872729d0
diff --git a/tools/cpplint.py b/tools/cpplint.py
index 4f069b7..0b5fb93 100755
--- a/tools/cpplint.py
+++ b/tools/cpplint.py
@@ -1206,7 +1206,6 @@
     ('gmtime(', 'gmtime_r('),
     ('localtime(', 'localtime_r('),
     ('rand(', 'rand_r('),
-    ('readdir(', 'readdir_r('),
     ('strtok(', 'strtok_r('),
     ('ttyname(', 'ttyname_r('),
     )