Add librdkafka to php8 modules
Add librdkafka to php8 modules

rdkafka now supports php8 and was added in a previous commit. rdkafka requires librdkafka.

cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci