[docs] `-fno-sanitize=` is accepted too.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184611 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/UsersManual.rst b/docs/UsersManual.rst
index 3622a17..9037047 100644
--- a/docs/UsersManual.rst
+++ b/docs/UsersManual.rst
@@ -853,7 +853,7 @@
 Clang provides a number of ways to control code generation. The options
 are listed below.
 
-**-fsanitize=check1,check2,...**
+**-f[no-]sanitize=check1,check2,...**
    Turn on runtime checks for various forms of undefined or suspicious
    behavior.