Bump ES 7.6 to lucene 8.3 (elastic#48273)

Updating lucene to version 8.3.0 for 7.6 bwc

Author: albertzaharovits

server/src/main/java/org/elasticsearch/Version.java

@@ -69,7 +69,7 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_7_4_0 = new Version(7040099, org.apache.lucene.util.Version.LUCENE_8_2_0);
     public static final Version V_7_4_1 = new Version(7040199, org.apache.lucene.util.Version.LUCENE_8_2_0);
     public static final Version V_7_5_0 = new Version(7050099, org.apache.lucene.util.Version.LUCENE_8_2_0);
-    public static final Version V_7_6_0 = new Version(7060099, org.apache.lucene.util.Version.LUCENE_8_2_0);
+    public static final Version V_7_6_0 = new Version(7060099, org.apache.lucene.util.Version.LUCENE_8_3_0);
     public static final Version V_8_0_0 = new Version(8000099, org.apache.lucene.util.Version.LUCENE_8_3_0);
     public static final Version CURRENT = V_8_0_0;