Fix 404: Snowball analyzer languages links

Could use the github-mirror links:
https://github.com/apache/lucene-solr/tree/branch_4x/lucene/analysis/common/src/resources/org/apache/lucene/analysis
and
https://github.com/apache/lucene-solr/tree/branch_4x/lucene/analysis/common/src/resources/org/apache/lucene/analysis/snowball