[Solr Wiki] Update of "ReleaseNote80" by datcm

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The "ReleaseNote80" page has been changed by datcm:
https://wiki.apache.org/solr/ReleaseNote80?action=diff&rev1=3&rev2=4

  
  == Solr 8.0.0 Release Highlights ==
  
- * Solr now uses HTTP/2 for inter-node communication
+ * Solr is switching from Apache HttpClient to Jetty Client for adding HTTP/2 support. Most frequent inter-communication between nodes like indexing and query are now sent in HTTP/2. HTTP/1.1 practically allows only one outstanding request per TCP connection this means that for sending multiple requests at the same time multiple TCP connections must be established. This leads to waste of resources on both-sides and long GC-pause. Solr 8 with HTTP/2 support overcomes that problem by allowing multiple requests can be sent in parallel using a same TCP connection.
  
  * Nested documents (AKA child documents or block join) is significantly improved.  Most improvements come from storing and leveraging more information about the relationships in the index, like the named relationship between a child and its parent.  This information is used by the [child] doc transformer to return children in nested form instead of flat.  There is plenty more that can be done with this in the future.  Another key improvement is that nested documents can be deleted or replaced in a natural way without orphaning child documents; although care is still needed with delete-by-query.