Form GridColumn is broken

# Bug Report

## Prerequisites

* [x] Can you reproduce the problem on TYPO3 v11.5 LTS
* [x] Can you reproduce the problem on TYPO3 v12.4 LTS
* [x] Did you [perform a cursory search](https://github.com/issues?q=is%3Aissue+user%3Abenjaminkott+repo%3Abenjaminkott%2Fbootstrap_package)
to see if your bug or enhancement is already reported?

## Description

Contact form is not rendered properly. All fields from grid columns are missing in html output.

## Steps to Reproduce

1. Add form ce
2. Choose 'Contact Form' from ext:bootstrap_package in plugin tab
3. Show the frontend

### Expected behavior

The full contact form is shown.

### Actual behavior

Only the header and submit button is shown.

## Versions

14.0.7

Reproduce the issue by adding a form content element, selecting the Contact Form from ext:bootstrap_package, and viewing the frontend. Trace the form rendering path for GridColumn and verify that all contact-form fields, not only the header and submit button, appear in the HTML output.

Written by the indexing model from the issue text.