No Text for "Navigation icon" folder button in v14

# Bug Report

## Prerequisites

* [x] Can you reproduce the problem on TYPO3 v14
* [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

The sys_file_reference Button does not have an accessible name (no textual representation).

## Steps to Reproduce

1. Go in TYPO3 Backend
2. Edit properties of a page
3. Inspect the "Folder" button of "Navigation Icon"

### Expected behavior

The button should have the label of the similar core button "Add image" - probably the location of the core language string has changed in v14

## Versions

TYPO3 v14

Start in the backend form configuration for the sys_file_reference field used by the Navigation Icon, and inspect how its Folder button gets its language label. Compare it with the core Add image button; done means the Folder button exposes a textual accessible name in TYPO3 v14.

Written by the indexing model from the issue text.