Fix PHP 8.4 deprecations [#3612245]

Problem/Motivation

ddev druPHP Deprecated: Drupal\media_fotoweb\Form\FotowebBrowserForm::__construct(): Implicitly marking parameter $opener_resolver as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/media_fotoweb/src/Form/FotowebBrowserForm.php on line 69

Deprecated: Drupal\media_fotoweb\Form\FotowebBrowserForm::__construct(): Implicitly marking parameter $opener_resolver as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/media_fotoweb/src/Form/FotowebBrowserForm.php on line 69
PHP Deprecated: Drupal\media_fotoweb\MediaFotowebLibraryUiBuilder::__construct(): Implicitly marking parameter $opener_resolver as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/media_fotoweb/src/MediaFotowebLibraryUiBuilder.php on line 35

Deprecated: Drupal\media_fotoweb\MediaFotowebLibraryUiBuilder::__construct(): Implicitly marking parameter $opener_resolver as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/web/modules/contrib/media_fotoweb/src/MediaFotowebLibraryUiBuilder.php on line 35

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Issue fork media_fotoweb-3612245

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3612245-fix-php-deprecations changes, plain diff MR !23
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