Help/dev: Update export policy version in post-release development

Since commit 20fa4ce8d8 (export: Factor out CMake-specific export
generation (2/2), 2024-07-18) the code that needs editing is in a
different method.

Help/dev/maint.rst

@@ -339,7 +339,7 @@ Commit with a message such as::
   away from setting policies to OLD.
 
 Update the ``cmake_policy`` version range generated by ``install(EXPORT)``
-in ``cmExportFileGenerator::GeneratePolicyHeaderCode`` and
+in ``cmExportCMakeConfigGenerator::GeneratePolicyHeaderCode`` and
 ``install_jar_exports`` in ``javaTargets.cmake.in`` to end at the
 previous release.  We use one release back since we now know all the
 policies added for that version.  Commit with a message such as::