Added bwc version 1.3.21 (#16835)

Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Signed-off-by: Andriy Redko <andriy.redko@aiven.io>
Co-authored-by: opensearch-ci-bot <83309141+opensearch-ci-bot@users.noreply.github.com>

Author: opensearch-trigger-bot[bot]

.ci/bwcVersions

@@ -105,3 +105,4 @@ BWC_VERSION:
   - "1.3.18"
   - "1.3.19"
   - "1.3.20"
+  - "1.3.21"

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

@@ -101,6 +101,7 @@ public class Version implements Comparable<Version>, ToXContentFragment {
     public static final Version V_1_3_18 = new Version(1031899, org.apache.lucene.util.Version.LUCENE_8_10_1);
     public static final Version V_1_3_19 = new Version(1031999, org.apache.lucene.util.Version.LUCENE_8_10_1);
     public static final Version V_1_3_20 = new Version(1032099, org.apache.lucene.util.Version.LUCENE_8_10_1);
+    public static final Version V_1_3_21 = new Version(1032199, org.apache.lucene.util.Version.LUCENE_8_10_1);
     public static final Version V_1_4_0 = new Version(1040099, org.apache.lucene.util.Version.LUCENE_8_10_1);
     public static final Version CURRENT = V_1_4_0;