remove ref to DP array indexing documentation from 4.5 docs

http://developer.couchbase.com/documentation/server/4.5/n1ql/n1ql-language-reference/createindex.html

'array indexing' link in the following note points to DP doc.

Note:
Couchbase Server 4.5 Developer Preview release adds the capability to create global indexes on array elements and optimizes the execution of queries involving array elements. See Array Indexing for details.