Upgrade to Lucene 7.4.0. (#31529)

This moves Elasticsearch from a recent 7.4.0 snapshot to the GA release.

Author: jpountz

buildSrc/version.properties

@@ -1,5 +1,5 @@
 elasticsearch     = 6.4.0
-lucene            = 7.4.0-snapshot-518d303506
+lucene            = 7.4.0
 
 # optional dependencies
 spatial4j         = 0.7

modules/lang-expression/licenses/lucene-expressions-7.4.0-snapshot-518d303506.jar.sha1

@@ -0,0 +1 @@
+9f0a326f7ec1671ffb07f95b27f1a5812b7dc1c3

modules/lang-expression/licenses/lucene-expressions-7.4.0.jar.sha1

@@ -0,0 +1 @@
+394e811e9d9bf0b9fba837f7ceca9e8f3e39d1c2

plugins/analysis-icu/licenses/lucene-analyzers-icu-7.4.0-snapshot-518d303506.jar.sha1

@@ -0,0 +1 @@
+5cd56acfa16ba20e19b5d21d90b510eada841431

plugins/analysis-icu/licenses/lucene-analyzers-icu-7.4.0.jar.sha1

@@ -0,0 +1 @@
+db7b56f4cf533ad9022d2312c5ee48331edccca3