use LATEST luceneMatchVersion in test/resources

[cpoerschke]

When running the tests locally I noticed warnings in the output e.g.

WARN  FieldTypePluginLoader  - TokenizerFactory is using deprecated 6.4.2 emulation. You should at some point declare and reindex to at least 7.0, because 6.x emulation is deprecated and will be removed in 8.0

• Increasing the tests' luceneMatchVersion version removes the warnings but I don't know if the versions currently in use are used for a specific reason or not?
• The spark-solr/src/main/resources/embedded/solrconfig.xml file e.g. https://github.com/lucidworks/spark-solr/blob/v3.7.6/src/main/resources/embedded/solrconfig.xml#L3 uses <luceneMatchVersion>LATEST</luceneMatchVersion> and if no specific version is intended or required for the tests then using LATEST could be an alternative too.
  • edit: it seems no specific version is required and so I've added a commit to use LATEST instead