What's new in Gerrit 2.8: Mention that Lucene is built-in

Mention that the Lucene functionality is built-in, but Solr
Cloud requires external setup.

Change-Id: I12466b5a4dfd76a5e7e788a4ccbed7e0aeb2cf90

presentations/gerrit-new-features-2.8/gerrit-new-features-2.8.txt

diff --git a/presentations/gerrit-new-features-2.8/gerrit-new-features-2.8.txt b/presentations/gerrit-new-features-2.8/gerrit-new-features-2.8.txt
index ff9e893..ffd4505 100644
--- a/presentations/gerrit-new-features-2.8/gerrit-new-features-2.8.txt
+++ b/presentations/gerrit-new-features-2.8/gerrit-new-features-2.8.txt
@@ -37,6 +37,8 @@
 
 * Lucene and Solr Cloud indexes are supported
 
+* Lucene is built-in; Solr Cloud requires external setup
+
 * In 2.8 the secondary index is optional
 
 * From 2.9 it will be mandatory; the default will be Lucene