Add 7.6.3 version

Author: jimczi

.ci/bwcVersions

@@ -17,6 +17,7 @@ BWC_VERSION:
   - "7.6.0"
   - "7.6.1"
   - "7.6.2"
+  - "7.6.3"
   - "7.7.0"
   - "7.8.0"
   - "8.0.0"

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

@@ -75,6 +75,7 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_7_6_0 = new Version(7060099, org.apache.lucene.util.Version.LUCENE_8_4_0);
     public static final Version V_7_6_1 = new Version(7060199, org.apache.lucene.util.Version.LUCENE_8_4_0);
     public static final Version V_7_6_2 = new Version(7060299, org.apache.lucene.util.Version.LUCENE_8_4_0);
+    public static final Version V_7_6_3 = new Version(7060399, org.apache.lucene.util.Version.LUCENE_8_4_0);
     public static final Version V_7_7_0 = new Version(7070099, org.apache.lucene.util.Version.LUCENE_8_5_0);
     public static final Version V_7_8_0 = new Version(7080099, org.apache.lucene.util.Version.LUCENE_8_5_0);
     public static final Version V_8_0_0 = new Version(8000099, org.apache.lucene.util.Version.LUCENE_8_5_0);