Allow dev versions of search_api_solr_multilingual to be used

Problem/Motivation

I've created a fork of search_api_solr_multilingual to allow a higher version of the maennchen/zipstream-php to be used.
Now creating a fork here to allow acquia_search to use this version.

Proposed resolution

See if we need to switch to a less fixed version number for search_api_solr_multilingual.

Remaining tasks

Check if everything works.