* Update basic-cluster-tuning.md
The sentence "When free system memory is greater than or equal to druid.segmentCache.locations, the more segment data the Historical can be held in the memory-mapped segment cache" didn't read well. Updated to clarify it.
* Update docs/operations/basic-cluster-tuning.md
* Update docs/operations/basic-cluster-tuning.md
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Co-authored-by: Charles Smith <techdocsmith@gmail.com>