[12] RFR: 8209652: Ensemble: Update version of Lucene to 7.4.0

[Kevin Rushforth]

Phil,

Please review the following:
https://bugs.openjdk.java.net/browse/JDK-8209652
http://cr.openjdk.java.net/~kcr/8209652/webrev/

This bumps the version of Apache Lucene used by Ensemble to the latest 
7.4.0 release.

-- Kevin