doc: build: version: update include path to app_version.h

Update include path note for app_version.h to match changes from PR zephyrproject-rtos#63973

Signed-off-by: Thomas Decker <decker@jb-lighting.de>

Author: TD-JBL

doc/build/version/index.rst

@@ -72,7 +72,7 @@ Use in code
 ===========
 
 To use the version information in application code, the version file must be included, then the
-fields can be freely used. The include file name is :file:`app_version.h` (no path is needed), the
+fields can be freely used. The include file name is :file:`app_version.h` (use ``#include <zephyr/app_version.h>``), the
 following defines are available:
 
 +-----------------------------+-------------------+------------------------------------------------------+---------------------------+