Fix typo in generated header name (#9034)

docs/source/languages/cpp.md

diff --git a/docs/source/languages/cpp.md b/docs/source/languages/cpp.md
index 445ca73..96be6a3 100644
--- a/docs/source/languages/cpp.md
+++ b/docs/source/languages/cpp.md
@@ -57,7 +57,7 @@
 
 ```cpp
     #include "flatbuffers/flatbuffers.h"
-    #include "monster_test_generate.h"
+    #include "monster_test_generated.h"
     #include <iostream> // C++ header file for printing
     #include <fstream> // C++ header file for file access