[TASK] Update solr version to v6.6.2

According to https://raw.githubusercontent.com/TYPO3-Solr/ext-solr/master/Documentation/Appendix/VersionMatrix.rst
ext:solr v7.5.0 requires solr v6.6.2.
3 jobs for ddev-0.18.0 in 6 minutes and 50 seconds (queued for 3 seconds)