Add ES version 6.4.3 (#34239)

Version bump

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

@@ -103,6 +103,8 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_6_4_1 = new Version(V_6_4_1_ID, org.apache.lucene.util.Version.LUCENE_7_4_0);
     public static final int V_6_4_2_ID = 6040299;
     public static final Version V_6_4_2 = new Version(V_6_4_2_ID, org.apache.lucene.util.Version.LUCENE_7_4_0);
+    public static final int V_6_4_3_ID = 6040399;
+    public static final Version V_6_4_3 = new Version(V_6_4_3_ID, org.apache.lucene.util.Version.LUCENE_7_4_0);
     public static final int V_6_5_0_ID = 6050099;
     public static final Version V_6_5_0 = new Version(V_6_5_0_ID, org.apache.lucene.util.Version.LUCENE_7_5_0);
     public static final int V_7_0_0_alpha1_ID = 7000001;
@@ -125,6 +127,8 @@ public class Version implements Comparable<Version>, ToXContentFragment {
                 return V_7_0_0_alpha1;
             case V_6_5_0_ID:
                 return V_6_5_0;
+            case V_6_4_3_ID:
+                return V_6_4_3;
             case V_6_4_2_ID:
                 return V_6_4_2;
             case V_6_4_1_ID: