RFR: 8260246: Ensemble: Update version of Lucene to 7.7.3

[Kevin Rushforth]

This updates to the latest bug fix version of Lucene 7, which is version 7.7.3. Since it is only an update to the micro version, there is no need to regenerate the index. See [UPDATING-lucene.txt](https://github.com/openjdk/jfx/blob/master/apps/samples/Ensemble8/UPDATING-lucene.txt).

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Commit messages:
 - 8260246: Ensemble: Update version of Lucene to 7.7.3

Changes: https://git.openjdk.java.net/jfx/pull/387/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=387&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260246
  Stats: 9 lines in 5 files changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jfx/pull/387.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/387/head:pull/387

PR: https://git.openjdk.java.net/jfx/pull/387