Update php ldap module in ddev environment

FollowUp to 19fbd96b

Currently a ddev composer install fails with

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - causal/ig_ldap_sso_auth 3.5.1 requires ext-ldap * -> the requested PHP extension ldap is missing from your system.
    - causal/ig_ldap_sso_auth 3.5.1 requires ext-ldap * -> the requested PHP extension ldap is missing from your system.
    - Installation request for causal/ig_ldap_sso_auth 3.5.1 -> satisfiable by causal/ig_ldap_sso_auth[3.5.1].

I tried to fix it by setting https://gitlab.typo3.org/t3o/typo3.org/-/blob/develop-v10/.ddev/config.yaml#L25 to webimage_extra_packages: [php7.4-ldap], but then ddev doesn't start.

As a workaround you can use --ignore-platform-reqs on ddev composer install and ddev composer require (like it's done in https://gitlab.typo3.org/t3o/typo3.org/-/blob/develop-v10/.ddev/config.yaml#L20)