[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.

.ddev/docker-compose.solr.yaml

@@ -11,7 +11,7 @@ version: '3'
 services:
   solr: # This is the service name used when running ddev commands accepting the --service flag
     container_name: ddev-${DDEV_SITENAME}-solr # This is the name of the container. It is recommended to follow the same name convention used in the main docker-compose.yml file.
-    image: solr:6.3.0
+    image: solr:6.6.2
     restart: always
     ports:
       - 8983 # Solr is served from this port inside the container
@@ -34,4 +34,4 @@ services:
 # This links the solr service to the web service defined in the main docker-compose.yml, allowing applications running in the web service to access the solr service at sitename.ddev.local:8983
   web:
     links:
-      - solr:$DDEV_HOSTNAME
\ No newline at end of file
+      - solr:$DDEV_HOSTNAME