Php 8.4 deprecation error [#3595223]

Problem/Motivation

PHP Deprecated:  Drupal\phone_number\PhoneNumberUtil::getCountryOptions(): Implicitly marking parameter $filter as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/docroot/modules/contrib/phone_number/src/PhoneNumberUtil.php on line 242
PHP Deprecated:  Drupal\phone_number\PhoneNumberUtilInterface::getCountryOptions(): Implicitly marking parameter $filter as nullable is deprecated, the explicit nullable type must be used instead in /var/www/html/docroot/modules/contrib/phone_number/src/PhoneNumberUtilInterface.php on line 193

Steps to reproduce

Proposed resolution

Install and enable php 8.4
Visit any of the node page

Remaining tasks

User interface changes

API changes

Data model changes

Issue fork phone_number-3595223

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3595223-php-8.4-deprecation changes, plain diff MR !47
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