Correct spelling of 'enumerator'.

Post commit code review feedback to r175705 from Jordan Rose.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175724 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/ADT/None.h b/include/llvm/ADT/None.h
index 83c9521..5793bd2 100644
--- a/include/llvm/ADT/None.h
+++ b/include/llvm/ADT/None.h
@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-//  This file provides None, an enumerant for use in implicit constructors
+//  This file provides None, an enumerator for use in implicit constructors
 //  of various (usually templated) types to make such construction more
 //  terse.
 //