Fix link

[tallison (Tim Allison)]

There's a bad link on the Similarity page:
https://www.elastic.co/guide/en/elasticsearch/reference/current/index-modules-similarity.html#lm_jelinek_mercer

The link to the Lucene documentation has an extra "core/"
http://lucene.apache.org/core/8_5_1/core/core/org/apache/lucene/search/similarities/LMJelinekMercerSimilarity.html

[spinscale (Alexander Reelsen)]

Hey Tim

thx for the ping! I opened https://github.com/elastic/elasticsearch/pull/59365

--Alex