Adding unreleased 5.6.3 version number to Version.java (#26794)

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

@@ -96,6 +96,8 @@ public class Version implements Comparable<Version> {
     public static final Version V_5_6_1 = new Version(V_5_6_1_ID, org.apache.lucene.util.Version.LUCENE_6_6_1);
     public static final int V_5_6_2_ID = 5060299;
     public static final Version V_5_6_2 = new Version(V_5_6_2_ID, org.apache.lucene.util.Version.LUCENE_6_6_1);
+    public static final int V_5_6_3_ID = 5060399;
+    public static final Version V_5_6_3 = new Version(V_5_6_3_ID, org.apache.lucene.util.Version.LUCENE_6_6_1);
     public static final int V_6_0_0_alpha1_ID = 6000001;
     public static final Version V_6_0_0_alpha1 =
             new Version(V_6_0_0_alpha1_ID, org.apache.lucene.util.Version.LUCENE_7_0_0);
@@ -146,6 +148,8 @@ public class Version implements Comparable<Version> {
                 return V_6_0_0_alpha2;
             case V_6_0_0_alpha1_ID:
                 return V_6_0_0_alpha1;
+            case V_5_6_3_ID:
+                return V_5_6_3;
             case V_5_6_2_ID:
                 return V_5_6_2;
             case V_5_6_1_ID: