Fix typo

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@342361 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__threading_support b/include/__threading_support
index 3c1eff2..2024900 100644
--- a/include/__threading_support
+++ b/include/__threading_support
@@ -70,7 +70,7 @@
 
 typedef pthread_t __libcpp_thread_t;
 
-// Thrad Local Storage
+// Thread Local Storage
 typedef pthread_key_t __libcpp_tls_key;
 
 #define _LIBCPP_TLS_DESTRUCTOR_CC