Update CI continuous-integration-user_saml_shibboleth-php8.0 image for master

[blizzz]

continuous-integration-user_saml_shibboleth-php8.0:latest is based on unicon/shibboleth-idp:3.4.3, which itself is based on CentOS 7. It ships sqlite 3.7 only, which errors on "SELECT * FROM PRAGMA_TABLE_INFO ("tablename");". System requirements specify RedHat 8 (=> CentOS 8) also.

unicon/shibboleth-idp is not maintained any longer either.