[Docs] Correct the path to the clang-format-diff.py script to include the clang-format directory.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@301202 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/ClangFormat.rst b/docs/ClangFormat.rst
index dc1e2b9..ed0e58e 100644
--- a/docs/ClangFormat.rst
+++ b/docs/ClangFormat.rst
@@ -162,8 +162,9 @@
 Script for patch reformatting
 =============================
 
-The python script `clang/tools/clang-format-diff.py` parses the output of
-a unified diff and reformats all contained lines with :program:`clang-format`.
+The python script `clang/tools/clang-format/clang-format-diff.py` parses the
+output of a unified diff and reformats all contained lines with
+:program:`clang-format`.
 
 .. code-block:: console