IWYU: Update for Debian 12 CI job

`include-what-you-use` diagnostics, in practice, are specific to
the environment's compiler and standard library.  Update includes
to satisfy IWYU for our CI job under Debian 12.

Source/cmInstallExportGenerator.h

@@ -10,7 +10,6 @@
 #include <vector>
 
 #include "cmInstallGenerator.h"
-#include "cmScriptGenerator.h"
 
 class cmExportInstallFileGenerator;
 class cmExportSet;