Force never_cache_twig on form modular child pages
Force never_cache_twig on form modular child pages

The `if` inside the header form property check was never reached.
At this point, the modular form info is already moved to the parent
page (modular.md) header. This change checks the template name, which
satisfies the default modular form usage.

getgrav/grav-plugin-form,getgrav/grav-plugin-form,getgrav/grav-plugin-form