Fix English grammar error.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184463 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Lex/ModuleMap.h b/include/clang/Lex/ModuleMap.h
index bd57ce4..b33b9e5 100644
--- a/include/clang/Lex/ModuleMap.h
+++ b/include/clang/Lex/ModuleMap.h
@@ -85,7 +85,7 @@
 
   typedef llvm::DenseMap<const FileEntry *, KnownHeader> HeadersMap;
 
-  /// \brief Mapping from each header to the module that owns the contents of the
+  /// \brief Mapping from each header to the module that owns the contents of
   /// that header.
   HeadersMap Headers;