fix typo


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@73304 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/UsersManual.html b/docs/UsersManual.html
index 5ee52f6..65415ee 100644
--- a/docs/UsersManual.html
+++ b/docs/UsersManual.html
@@ -455,7 +455,7 @@
 for headers that are directly included within a source file. For example:</p>
 
 <pre>
-  $ clang -x c-header test.h -o test.h.cth
+  $ clang -x c-header test.h -o test.h.pch
   $ cat test.c
   #include "test.h"
   $ clang test.c -o test