DOCS-953 release notes edits to text search info

Author: kay-kim

source/release-notes/2.4.txt

@@ -157,9 +157,12 @@ To create a ``text`` index, use the following invocation of
 
    db.collection.ensureIndex( { content: "text" } )
 
-``text`` indexes catalog all string data in the ``content`` field. Your
-``text`` index can include content from multiple fields, or arrays,
-and from fields in sub-documents, as in the following:
+This ``text`` index catalogs all string data in the ``content`` field
+where the ``content`` field contains a string or an array of string
+elements. To index fields in sub-documents, you need to specify the
+individual fields from the sub-documents using the :term:`dot
+notation`. A ``text`` index can include multiple fields, as in the
+following:
 
 .. code-block:: javascript